From 329f0dbfa3a164ee2e3bf9f75b7641165995c799 Mon Sep 17 00:00:00 2001
From: Jeff Handley <jeffhandley@users.noreply.github.com>
Date: Fri, 17 Jul 2020 17:09:29 -0700
Subject: [PATCH] Mark Obsoletions for .NET 5 (#39269)

* Mark new obsoletions for .NET 5; update existing obsoletions

* Exclude DirectoryServicesPermission/DirectoryServicesPermissionAttribute from obsoletions for now

* No need to restore SYSLIB0003 at end of Forwards files

* Use a common Obsoletions.cs file for all SYSLIB obsoletions

* Resurrect CER code behind #ifdef in EventSource

* Mark GlobalAssemblyCache overrides as Obsolete

* Suppress Thread.Abort() error in ImageAnimator.Unix.cs

* Unconditionally mark RoAssembly.GlobalAssemblyCache as obsolete

* Rename MSLIB0001 to SYSLIB0001 in ref assembly

* Suppress obsoletion warnings in tests

* Adopt a uniform #ifdef for NET50_OBSOLETIONS

* Fix BinaryFormatter obsoletion message after the rebase

* Use SYSTEM_PRIVATE_CORELIB constant instead of NETCOREAPP

* Remove the code comment on the ifdef

* Apply feedback related to CER obsoletions

* Apply feedback related to CAS

* Update ref assembly to reflect SecurityManager obsoletion

* Fix regression in System.IO.Pipes.NamedPipeServerStream.Windows.RunAsClient
---
 docs/project/list-of-obsoletions.md           |  24 +-
 .../System/Reflection/Emit/AssemblyBuilder.cs |   1 +
 .../src/System/Reflection/RuntimeAssembly.cs  |   1 +
 .../System/Diagnostics/NetFrameworkUtils.cs   |   2 +-
 .../Common/src/System/Obsoletions.cs          |  43 ++
 .../System/Buffers/BoundedMemory.Windows.cs   |   1 -
 src/libraries/Directory.Build.props           |   2 +-
 src/libraries/Directory.Build.targets         |   3 +
 .../src/Microsoft.Win32.SystemEvents.csproj   |   2 +
 .../src/Microsoft/Win32/SystemEvents.cs       |   2 +
 .../DesigntimeLicenseContextSerializer.cs     |   8 +-
 .../System/Configuration/TypeUtilTests.cs     |   2 +
 .../src/System/Data/DataSet.cs                |   8 +-
 .../System/Data/Common/AdapterUtil.Odbc.cs    |   1 -
 .../System/Data/ProviderBase/DbBuffer.cs      |  46 +-
 .../src/System/Data/Odbc/OdbcCommand.cs       |   1 -
 .../System/Data/Odbc/OdbcConnectionHandle.cs  |   9 +-
 .../src/System/Data/Odbc/OdbcDataReader.cs    |   2 -
 .../src/System/Data/Odbc/OdbcHandle.cs        |   4 +-
 .../src/System/Diagnostics/EventLog.cs        |   3 -
 .../System/Diagnostics/EventLogInternal.cs    |   2 +-
 .../Diagnostics/Reader/UnsafeNativeMethods.cs |   1 -
 .../Protocols/ldap/LdapSessionOptions.cs      |   2 -
 .../DirectoryServicesPermission.cs            |   4 +
 .../DirectoryServicesPermissionAttribute.cs   |   4 +
 .../System.DirectoryServices.Tests.csproj     |   3 +-
 .../BufferedGraphicsManager.Windows.cs        |   1 -
 .../src/System/Drawing/Graphics.Windows.cs    |   1 -
 .../src/System/Drawing/ImageAnimator.Unix.cs  |   2 +
 .../IO/Pipes/NamedPipeServerStream.Windows.cs |  17 +-
 .../tests/Support/PortsTest.cs                |   4 +-
 .../ref/System.Linq.Expressions.cs            |   1 +
 .../src/System.Linq.Expressions.csproj        |   2 +
 .../CompilerServices/DebugInfoGenerator.cs    |   1 +
 .../ref/System.Net.Requests.cs                |   2 +
 .../src/System.Net.Requests.csproj            |   2 +
 .../src/System/Net/AuthenticationManager.cs   |   2 +
 .../tests/AuthenticationManagerTest.cs        |   2 +
 .../System.Private.CoreLib.Shared.projitems   |   4 +-
 .../src/System/AppDomain.cs                   |   1 +
 .../TraceLogging/TraceLoggingEventSource.cs   |   6 +-
 .../src/System/MarshalByRefObject.cs          |   2 +
 .../src/System/Obsoletions.cs                 |  13 -
 .../src/System/Reflection/Assembly.cs         |   1 +
 .../CompilerServices/RuntimeHelpers.cs        |   5 +
 .../Runtime/ConstrainedExecution/Cer.cs       |   1 +
 .../ConstrainedExecution/Consistency.cs       |   1 +
 .../PrePrepareMethodAttribute.cs              |   1 +
 .../ReliabilityContractAttribute.cs           |   1 +
 .../src/System/Security/IPermission.cs        |   1 +
 .../src/System/Security/IStackWalk.cs         |   3 +
 .../src/System/Security/PermissionSet.cs      |   3 +
 .../CodeAccessSecurityAttribute.cs            |   1 +
 .../Security/Permissions/PermissionState.cs   |   3 +
 .../Security/Permissions/SecurityAction.cs    |   5 +-
 .../Security/Permissions/SecurityAttribute.cs |   1 +
 .../SecurityPermissionAttribute.cs            |   1 +
 .../Permissions/SecurityPermissionFlag.cs     |   1 +
 .../src/System/Text/Encoding.cs               |   4 +-
 .../src/System/Text/UTF7Encoding.cs           |   4 +-
 .../src/System/Threading/Thread.cs            |   2 +
 .../System/Xml/Serialization/Compilation.cs   |   5 +-
 .../ref/System.Reflection.Emit.cs             |   1 +
 .../src/System.Reflection.Metadata.csproj     |   4 +-
 .../MemoryBlocks/MemoryMappedFileBlock.cs     |  14 +-
 .../MemoryBlocks/NativeHeapMemoryBlock.cs     |  14 +-
 .../Internal/Utilities/PinnedObject.cs        |   9 +-
 .../Metadata/Internal/VirtualHeap.cs          |  14 +-
 ...stem.Reflection.MetadataLoadContext.csproj |   4 +
 .../TypeLoading/Assemblies/RoAssembly.cs      |   3 +
 ...eflection.MetadataLoadContext.Tests.csproj |   2 +
 .../System.Reflection/tests/AssemblyTests.cs  |   2 +
 .../ref/System.Runtime.Extensions.Forwards.cs |   2 +
 .../tests/System/AppDomainTests.cs            |   2 +
 .../tests/System/MarshalByRefObjectTest.cs    |   2 +
 ...System.Runtime.Serialization.Formatters.cs |  12 +-
 ...em.Runtime.Serialization.Formatters.csproj |   3 +-
 .../System/Runtime/Serialization/Formatter.cs |   4 +-
 .../Formatters/Binary/BinaryFormatter.Core.cs |   4 +-
 .../BinaryFormatter.PlatformNotSupported.cs   |   4 +-
 .../Runtime/Serialization/IFormatter.cs       |   4 +-
 .../Runtime/Serialization/Obsoletions.cs      |  13 -
 .../tests/BinaryFormatterTestData.cs          |   2 +
 .../System.Runtime/ref/System.Runtime.cs      |  28 +-
 .../PrePrepareMethodAttributeTests.cs         |   2 +
 .../tests/System/Text/EncodingTests.cs        |   4 +-
 ...System.Security.Cryptography.Primitives.cs |   5 +
 ...em.Security.Cryptography.Primitives.csproj |   2 +
 .../Cryptography/AsymmetricAlgorithm.cs       |   1 +
 .../src/System/Security/Cryptography/HMAC.cs  |   1 +
 .../Security/Cryptography/HashAlgorithm.cs    |   1 +
 .../Cryptography/KeyedHashAlgorithm.cs        |   1 +
 .../Cryptography/SymmetricAlgorithm.cs        |   1 +
 .../tests/CryptoConfigTests.cs                |   2 +
 .../System.Security.Permissions.Forwards.cs   |   1 +
 .../ref/System.Security.Permissions.cs        | 396 +++++++++++++++++-
 .../ref/System.Security.Permissions.csproj    |   5 +-
 .../System.Security.Permissions.netcoreapp.cs |   3 +
 .../src/System.Security.Permissions.csproj    |   7 +-
 .../Configuration/ConfigurationPermission.cs  |   3 +
 .../System/Data/Common/DBDataPermission.cs    |   3 +
 .../src/System/Data/Odbc/OdbcPermission.cs    |   3 +
 .../src/System/Data/OleDb/OleDbPermission.cs  |   3 +
 .../Data/OracleClient/OraclePermission.cs     |   3 +
 .../Data/SqlClient/SqlClientPermission.cs     |   3 +
 .../System/Diagnostics/EventLogPermission.cs  |   3 +
 .../PerformanceCounterPermission.cs           |   3 +
 .../Drawing/Printing/PrintingPermission.cs    |   3 +
 .../src/System/Net/DnsPermission.cs           |   3 +
 .../src/System/Net/Mail/SmtpPermission.cs     |   3 +
 .../NetworkInformationPermission.cs           |   3 +
 .../PeerCollaborationPermission.cs            |   3 +
 .../System/Net/PeerToPeer/PnrpPermission.cs   |   3 +
 .../src/System/Net/SocketPermission.cs        |   3 +
 .../src/System/Net/WebPermission.cs           |   3 +
 .../Security/HostProtectionException.cs       |   3 +
 .../Permissions/DataProtectionPermission.cs   |   3 +
 .../DataProtectionPermissionAttribute.cs      |   3 +
 .../DataProtectionPermissionFlags.cs          |   3 +
 .../Permissions/EnvironmentPermission.cs      |   3 +
 .../EnvironmentPermissionAccess.cs            |   3 +
 .../EnvironmentPermissionAttribute.cs         |   3 +
 .../Permissions/FileDialogPermission.cs       |   3 +
 .../Permissions/FileDialogPermissionAccess.cs |   3 +
 .../FileDialogPermissionAttribute.cs          |   3 +
 .../Security/Permissions/FileIOPermission.cs  |   3 +
 .../Permissions/FileIOPermissionAccess.cs     |   3 +
 .../Permissions/FileIOPermissionAttribute.cs  |   3 +
 .../Permissions/GacIdentityPermission.cs      |   3 +
 .../GacIdentityPermissionAttribute.cs         |   3 +
 .../Permissions/HostProtectionAttribute.cs    |   3 +
 .../Permissions/HostProtectionResource.cs     |   3 +
 .../Permissions/IUnrestrictedPermission.cs    |   3 +
 .../Permissions/IsolatedStorageContainment.cs |   3 +
 .../IsolatedStorageFilePermission.cs          |   3 +
 .../IsolatedStorageFilePermissionAttribute.cs |   3 +
 .../Permissions/IsolatedStoragePermission.cs  |   3 +
 .../IsolatedStoragePermissionAttribute.cs     |   3 +
 .../Permissions/KeyContainerPermission.cs     |   3 +
 .../KeyContainerPermissionAccessEntry.cs      |   3 +
 ...ontainerPermissionAccessEntryCollection.cs |   3 +
 ...ontainerPermissionAccessEntryEnumerator.cs |   3 +
 .../KeyContainerPermissionAttribute.cs        |   3 +
 .../KeyContainerPermissionFlags.cs            |   3 +
 .../Security/Permissions/MediaPermission.cs   |  19 +
 .../Permissions/PermissionSetAttribute.cs     |   3 +
 .../Permissions/PrincipalPermission.cs        |   3 +
 .../PrincipalPermissionAttribute.cs           |   7 +-
 .../PublisherIdentityPermission.cs            |   3 +
 .../PublisherIdentityPermissionAttribute.cs   |   3 +
 .../Permissions/ReflectionPermission.cs       |   3 +
 .../ReflectionPermissionAttribute.cs          |   3 +
 .../Permissions/ReflectionPermissionFlag.cs   |   3 +
 .../Permissions/RegistryPermission.cs         |   3 +
 .../Permissions/RegistryPermissionAccess.cs   |   3 +
 .../RegistryPermissionAttribute.cs            |   3 +
 .../Permissions/ResourcePermissionBase.cs     |   3 +
 .../ResourcePermissionBaseEntry.cs            |   3 +
 .../Permissions/SecurityPermission.cs         |   3 +
 .../Permissions/SiteIdentityPermission.cs     |   3 +
 .../SiteIdentityPermissionAttribute.cs        |   3 +
 .../Security/Permissions/StorePermission.cs   |   3 +
 .../Permissions/StorePermissionAttribute.cs   |   3 +
 .../Permissions/StorePermissionFlags.cs       |   3 +
 .../StrongNameIdentityPermission.cs           |   3 +
 .../StrongNameIdentityPermissionAttribute.cs  |   3 +
 .../Permissions/StrongNamePublicKeyBlob.cs    |   3 +
 .../Permissions/TypeDescriptorPermission.cs   |   3 +
 .../TypeDescriptorPermissionAttribute.cs      |   3 +
 .../TypeDescriptorPermissionFlags.cs          |   3 +
 .../Security/Permissions/UIPermission.cs      |   3 +
 .../Permissions/UIPermissionAttribute.cs      |   3 +
 .../Permissions/UIPermissionClipboard.cs      |   3 +
 .../Permissions/UIPermissionWindow.cs         |   3 +
 .../Permissions/UrlIdentityPermission.cs      |   3 +
 .../UrlIdentityPermissionAttribute.cs         |   3 +
 .../Permissions/WebBrowserPermission.cs       |  10 +
 .../Permissions/ZoneIdentityPermission.cs     |   3 +
 .../ZoneIdentityPermissionAttribute.cs        |   3 +
 .../Security/Policy/ApplicationTrust.cs       |   6 +
 .../System/Security/Policy/FileCodeGroup.cs   |   3 +
 .../src/System/Security/Policy/StrongName.cs  |   3 +
 .../Policy/StrongNameMembershipCondition.cs   |   3 +
 .../src/System/Security/SecurityManager.cs    |   3 +
 .../ServiceControllerPermission.cs            |   3 +
 .../DistributedTransactionPermission.cs       |   3 +
 .../src/System/Web/AspNetHostingPermission.cs |   3 +
 .../Xaml/Permissions/XamlLoadPermission.cs    |   3 +
 .../System.Security.Permissions.Tests.csproj  |   2 +
 .../ref/System.Text.Encoding.Extensions.cs    |   4 +-
 .../tests/System.Text.Encoding.Tests.csproj   |   2 +-
 .../ref/System.Threading.Thread.cs            |   2 +
 .../tests/ThreadTests.cs                      |   4 +-
 .../Reflection/Emit/AssemblyBuilder.Mono.cs   |   1 +
 .../src/System/Reflection/RuntimeAssembly.cs  |   1 +
 195 files changed, 997 insertions(+), 183 deletions(-)
 create mode 100644 src/libraries/Common/src/System/Obsoletions.cs
 delete mode 100644 src/libraries/System.Private.CoreLib/src/System/Obsoletions.cs
 delete mode 100644 src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Obsoletions.cs

diff --git a/docs/project/list-of-obsoletions.md b/docs/project/list-of-obsoletions.md
index 6b4d3a415ef89..3b7d6696c62da 100644
--- a/docs/project/list-of-obsoletions.md
+++ b/docs/project/list-of-obsoletions.md
@@ -3,16 +3,24 @@ List of Obsoletions
 
 Per https://github.com/dotnet/designs/blob/master/accepted/2020/better-obsoletion/better-obsoletion.md, we now have a strategy in place for marking existing APIs as `[Obsolete]`. This takes advantage of the new diagnostic id and URL template mechanisms introduced to `ObsoleteAttribute` in .NET 5.
 
-When obsoleting an API, use the diagnostic ID `MSLIB####`, where _\#\#\#\#_ is the next four-digit identifier in the sequence, and add it to the list below. This helps us maintain a centralized location of all APIs that were obsoleted using this mechanism.
+When obsoleting an API, use the diagnostic ID `SYSLIB####`, where _\#\#\#\#_ is the next four-digit identifier in the sequence, and add it to the list below. This helps us maintain a centralized location of all APIs that were obsoleted using this mechanism.
 
 The URL template we use for obsoletions is `https://aka.ms/dotnet-warnings/{0}`.
 
-Currently the identifiers `MSLIB0001` through `MSLIB0999` are carved out for obsoletions. If we wish to introduce analyzer warnings not related to obsoletion in the future, we should begin at a different range, such as `MSLIB2000`.
+Currently the identifiers `SYSLIB0001` through `SYSLIB0999` are carved out for obsoletions. If we wish to introduce analyzer warnings not related to obsoletion in the future, we should begin at a different range, such as `SYSLIB2000`.
 
-## Current obsoletions (`MSLIB0001` - `MSLIB0999`)
+## Current obsoletions (`SYSLIB0001` - `SYSLIB0999`)
 
-| Diagnostic ID    | Description |
-| :--------------- | :---------- |
-|  __`MSLIB0001`__ | The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead. |
-|  __`MSLIB0002`__ | `PrincipalPermissionAttribute` is not honored by the runtime and must not be used. |
-|  __`MSLIB0003`__ | `BinaryFormatter` serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for recommended alternatives. |
+| Diagnostic ID     | Description |
+| :---------------- | :---------- |
+|  __`SYSLIB0001`__ | The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead. |
+|  __`SYSLIB0002`__ | PrincipalPermissionAttribute is not honored by the runtime and must not be used. |
+|  __`SYSLIB0003`__ | Code Access Security is not supported or honored by the runtime. |
+|  __`SYSLIB0004`__ | The Constrained Execution Region (CER) feature is not supported. |
+|  __`SYSLIB0005`__ | The Global Assembly Cache is not supported. |
+|  __`SYSLIB0006`__ | Thread.Abort is not supported and throws PlatformNotSupportedException. |
+|  __`SYSLIB0007`__ | The default implementation of this cryptography algorithm is not supported. |
+|  __`SYSLIB0008`__ | The CreatePdbGenerator API is not supported and throws PlatformNotSupportedException. |
+|  __`SYSLIB0009`__ | The AuthenticationManager Authenticate and PreAuthenticate methods are not supported and throw PlatformNotSupportedException. |
+|  __`SYSLIB0010`__ | This Remoting API is not supported and throws PlatformNotSupportedException. |
+|  __`SYSLIB0011`__ | `BinaryFormatter` serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for recommended alternatives. |
diff --git a/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs b/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs
index b71b9aba47146..e1ce8a9f61f92 100644
--- a/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs
+++ b/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.cs
@@ -499,6 +499,7 @@ public override AssemblyName[] GetReferencedAssemblies()
             return InternalAssembly.GetReferencedAssemblies();
         }
 
+        [Obsolete(Obsoletions.GlobalAssemblyCacheMessage, DiagnosticId = Obsoletions.GlobalAssemblyCacheDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public override bool GlobalAssemblyCache => InternalAssembly.GlobalAssemblyCache;
 
         public override long HostContext => InternalAssembly.HostContext;
diff --git a/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs b/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
index 6387b7e42fa4f..4aa7b486c723f 100644
--- a/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
+++ b/src/coreclr/src/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
@@ -451,6 +451,7 @@ public override string ImageRuntimeVersion
             }
         }
 
+        [Obsolete(Obsoletions.GlobalAssemblyCacheMessage, DiagnosticId = Obsoletions.GlobalAssemblyCacheDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public override bool GlobalAssemblyCache => false;
 
         public override long HostContext => 0;
diff --git a/src/libraries/Common/src/System/Diagnostics/NetFrameworkUtils.cs b/src/libraries/Common/src/System/Diagnostics/NetFrameworkUtils.cs
index 1c86656b12c77..4bab9a4590c35 100644
--- a/src/libraries/Common/src/System/Diagnostics/NetFrameworkUtils.cs
+++ b/src/libraries/Common/src/System/Diagnostics/NetFrameworkUtils.cs
@@ -63,7 +63,7 @@ private static bool SafeWaitForMutex(Mutex mutexIn, ref Mutex mutexOut)
         private static bool SafeWaitForMutexOnce(Mutex mutexIn, ref Mutex mutexOut)
         {
             bool ret;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             { }
             finally
diff --git a/src/libraries/Common/src/System/Obsoletions.cs b/src/libraries/Common/src/System/Obsoletions.cs
new file mode 100644
index 0000000000000..a7c5582f7bd8d
--- /dev/null
+++ b/src/libraries/Common/src/System/Obsoletions.cs
@@ -0,0 +1,43 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System
+{
+    internal static class Obsoletions
+    {
+        internal const string SharedUrlFormat = "https://aka.ms/dotnet-warnings/{0}";
+
+        internal const string SystemTextEncodingUTF7Message = "The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.";
+        internal const string SystemTextEncodingUTF7DiagId = "SYSLIB0001";
+
+        internal const string PrincipalPermissionAttributeMessage = "PrincipalPermissionAttribute is not honored by the runtime and must not be used.";
+        internal const string PrincipalPermissionAttributeDiagId = "SYSLIB0002";
+
+        internal const string CodeAccessSecurityMessage = "Code Access Security is not supported or honored by the runtime.";
+        internal const string CodeAccessSecurityDiagId = "SYSLIB0003";
+
+        internal const string ConstrainedExecutionRegionMessage = "The Constrained Execution Region (CER) feature is not supported.";
+        internal const string ConstrainedExecutionRegionDiagId = "SYSLIB0004";
+
+        internal const string GlobalAssemblyCacheMessage = "The Global Assembly Cache is not supported.";
+        internal const string GlobalAssemblyCacheDiagId = "SYSLIB0005";
+
+        internal const string ThreadAbortMessage = "Thread.Abort is not supported and throws PlatformNotSupportedException.";
+        internal const string ThreadAbortDiagId = "SYSLIB0006";
+
+        internal const string DefaultCryptoAlgorithmsMessage = "The default implementation of this cryptography algorithm is not supported.";
+        internal const string DefaultCryptoAlgorithmsDiagId = "SYSLIB0007";
+
+        internal const string CreatePdbGeneratorMessage = "The CreatePdbGenerator API is not supported and throws PlatformNotSupportedException.";
+        internal const string CreatePdbGeneratorDiagId = "SYSLIB0008";
+
+        internal const string AuthenticationManagerMessage = "The AuthenticationManager Authenticate and PreAuthenticate methods are not supported and throw PlatformNotSupportedException.";
+        internal const string AuthenticationManagerDiagId = "SYSLIB0009";
+
+        internal const string RemotingApisMessage = "This Remoting API is not supported and throws PlatformNotSupportedException.";
+        internal const string RemotingApisDiagId = "SYSLIB0010";
+
+        internal const string BinaryFormatterMessage = "BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.";
+        internal const string BinaryFormatterDiagId = "SYSLIB0011";
+    }
+}
diff --git a/src/libraries/Common/tests/TestUtilities/System/Buffers/BoundedMemory.Windows.cs b/src/libraries/Common/tests/TestUtilities/System/Buffers/BoundedMemory.Windows.cs
index 6b405a974a358..ba28f79a04ec2 100644
--- a/src/libraries/Common/tests/TestUtilities/System/Buffers/BoundedMemory.Windows.cs
+++ b/src/libraries/Common/tests/TestUtilities/System/Buffers/BoundedMemory.Windows.cs
@@ -305,7 +305,6 @@ public static extern VirtualAllocHandle VirtualAlloc(
 
             // https://msdn.microsoft.com/en-us/library/windows/desktop/aa366892(v=vs.85).aspx
             [DllImport(KERNEL32_LIB, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
-            [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
             [return: MarshalAs(UnmanagedType.Bool)]
             public static extern bool VirtualFree(
                 [In] IntPtr lpAddress,
diff --git a/src/libraries/Directory.Build.props b/src/libraries/Directory.Build.props
index c46cdcdb3b190..834d3a24ce7cb 100644
--- a/src/libraries/Directory.Build.props
+++ b/src/libraries/Directory.Build.props
@@ -63,7 +63,7 @@
   <!-- Warnings that should be disabled in our test projects. -->
   <PropertyGroup Condition="'$(IsTestProject)' == 'true' or '$(IsTestSupportProject)' == 'true'">
     <!-- don't warn on usage of BinaryFormatter from test projects -->
-    <NoWarn>$(NoWarn);MSLIB0003</NoWarn>
+    <NoWarn>$(NoWarn);SYSLIB0011</NoWarn>
   </PropertyGroup>
 
   <!-- Common repo directories -->
diff --git a/src/libraries/Directory.Build.targets b/src/libraries/Directory.Build.targets
index bf87a4ecc83ac..15be91dbe1c68 100644
--- a/src/libraries/Directory.Build.targets
+++ b/src/libraries/Directory.Build.targets
@@ -8,6 +8,9 @@
   <PropertyGroup>
     <NoWarn Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework' or '$(TargetFrameworkIdentifier)' == '.NETStandard' or '$(TargetFramework)' == 'netcoreapp2.1'">$(NoWarn);nullable</NoWarn>
     <NoWarn Condition="'$(GeneratePlatformNotSupportedAssembly)' == 'true' or '$(GeneratePlatformNotSupportedAssemblyMessage)' != ''">$(NoWarn);nullable</NoWarn>
+    <!-- Ignore Obsolete errors within the generated shims that type-forward types.
+         SYSLIB0003 is for CAS. SYSLIB0004 is the obsoletion of CER. -->
+    <NoWarn Condition="'$(IsPartialFacadeAssembly)' == 'true'">$(NoWarn);SYSLIB0003;SYSLIB0004</NoWarn>
     <!-- Reset these properties back to blank, since they are defaulted by Microsoft.NET.Sdk -->
     <FileAlignment Condition="'$(FileAlignment)' == '512'" />
     <ErrorReport Condition="'$(ErrorReport)' == 'prompt'" />
diff --git a/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft.Win32.SystemEvents.csproj b/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft.Win32.SystemEvents.csproj
index 0470f8b07a796..ba2d1c66aa26a 100644
--- a/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft.Win32.SystemEvents.csproj
+++ b/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft.Win32.SystemEvents.csproj
@@ -8,6 +8,8 @@
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
+    <!-- Constrained Execution Regions only apply to netstandard2.0 and net4* -->
+    <DefineConstants Condition="$(TargetFramework.StartsWith('netstandard2.0')) or $(TargetFramework.StartsWith('net4'))">$(DefineConstants);FEATURE_CER</DefineConstants>
     <IsPartialFacadeAssembly Condition="$(TargetFramework.StartsWith('net4'))">true</IsPartialFacadeAssembly>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetFramework)' == 'netstandard2.0' and '$(TargetsAnyOS)' == 'true'">SR.PlatformNotSupported_SystemEvents</GeneratePlatformNotSupportedAssemblyMessage>
   </PropertyGroup>
diff --git a/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft/Win32/SystemEvents.cs b/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft/Win32/SystemEvents.cs
index 4e1e0aac08862..ef4047801ab67 100644
--- a/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft/Win32/SystemEvents.cs
+++ b/src/libraries/Microsoft.Win32.SystemEvents/src/Microsoft/Win32/SystemEvents.cs
@@ -1114,7 +1114,9 @@ private static void Shutdown()
             }
         }
 
+#if FEATURE_CER
         [PrePrepareMethod]
+#endif
         private static void Shutdown(object? sender, EventArgs e)
         {
             Shutdown();
diff --git a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/Design/DesigntimeLicenseContextSerializer.cs b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/Design/DesigntimeLicenseContextSerializer.cs
index 137e2d91951f9..c4e7c24165e77 100644
--- a/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/Design/DesigntimeLicenseContextSerializer.cs
+++ b/src/libraries/System.ComponentModel.TypeConverter/src/System/ComponentModel/Design/DesigntimeLicenseContextSerializer.cs
@@ -26,18 +26,18 @@ private DesigntimeLicenseContextSerializer()
         public static void Serialize(Stream o, string cryptoKey, DesigntimeLicenseContext context)
         {
             IFormatter formatter = new BinaryFormatter();
-#pragma warning disable MSLIB0003 // Issue https://github.com/dotnet/runtime/issues/39293 tracks finding an alternative to BinaryFormatter
+#pragma warning disable SYSLIB0011 // Issue https://github.com/dotnet/runtime/issues/39293 tracks finding an alternative to BinaryFormatter
             formatter.Serialize(o, new object[] { cryptoKey, context._savedLicenseKeys });
-#pragma warning restore MSLIB0003
+#pragma warning restore SYSLIB0011
         }
 
         internal static void Deserialize(Stream o, string cryptoKey, RuntimeLicenseContext context)
         {
-#pragma warning disable MSLIB0003 // Issue https://github.com/dotnet/runtime/issues/39293 tracks finding an alternative to BinaryFormatter
+#pragma warning disable SYSLIB0011 // Issue https://github.com/dotnet/runtime/issues/39293 tracks finding an alternative to BinaryFormatter
             IFormatter formatter = new BinaryFormatter();
 
             object obj = formatter.Deserialize(o);
-#pragma warning restore MSLIB0003
+#pragma warning restore SYSLIB0011
 
             if (obj is object[] value)
             {
diff --git a/src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/TypeUtilTests.cs b/src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/TypeUtilTests.cs
index cc4817cdcd0ea..52da2e86daa70 100644
--- a/src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/TypeUtilTests.cs
+++ b/src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/TypeUtilTests.cs
@@ -317,10 +317,12 @@ bool IInternalConfigHost.IsTrustedConfigPath(string configPath)
                 throw new NotImplementedException();
             }
 
+#pragma warning disable SYSLIB0003 // Obsolete: CAS
             void IInternalConfigHost.GetRestrictedPermissions(IInternalConfigRecord configRecord, out PermissionSet permissionSet, out bool isHostReady)
             {
                 throw new NotImplementedException();
             }
+#pragma warning restore SYSLIB0003 // Obsolete: CAS
         }
     }
 }
diff --git a/src/libraries/System.Data.Common/src/System/Data/DataSet.cs b/src/libraries/System.Data.Common/src/System/Data/DataSet.cs
index 6ade9cb9fa7e6..10e27f30cbbc7 100644
--- a/src/libraries/System.Data.Common/src/System/Data/DataSet.cs
+++ b/src/libraries/System.Data.Common/src/System/Data/DataSet.cs
@@ -304,9 +304,9 @@ private void SerializeDataSet(SerializationInfo info, StreamingContext context,
                     {
                         BinaryFormatter bf = new BinaryFormatter(null, new StreamingContext(context.State, false));
                         MemoryStream memStream = new MemoryStream();
-#pragma warning disable MSLIB0003 // Issue https://github.com/dotnet/runtime/issues/39289 tracks finding an alternative to BinaryFormatter
+#pragma warning disable SYSLIB0011 // Issue https://github.com/dotnet/runtime/issues/39289 tracks finding an alternative to BinaryFormatter
                         bf.Serialize(memStream, Tables[i]);
-#pragma warning restore MSLIB0003
+#pragma warning restore SYSLIB0011
                         memStream.Position = 0;
                         info.AddValue(string.Format(CultureInfo.InvariantCulture, "DataSet.Tables_{0}", i), memStream.GetBuffer());
                     }
@@ -384,9 +384,9 @@ private void DeserializeDataSetSchema(SerializationInfo info, StreamingContext c
                         MemoryStream memStream = new MemoryStream(buffer);
                         memStream.Position = 0;
                         BinaryFormatter bf = new BinaryFormatter(null, new StreamingContext(context.State, false));
-#pragma warning disable MSLIB0003 // Issue https://github.com/dotnet/runtime/issues/39289 tracks finding an alternative to BinaryFormatter
+#pragma warning disable SYSLIB0011 // Issue https://github.com/dotnet/runtime/issues/39289 tracks finding an alternative to BinaryFormatter
                         DataTable dt = (DataTable)bf.Deserialize(memStream);
-#pragma warning restore MSLIB0003
+#pragma warning restore SYSLIB0011
                         Tables.Add(dt);
                     }
 
diff --git a/src/libraries/System.Data.Odbc/src/Common/System/Data/Common/AdapterUtil.Odbc.cs b/src/libraries/System.Data.Odbc/src/Common/System/Data/Common/AdapterUtil.Odbc.cs
index 8fe7210b7b696..de295724ab8a4 100644
--- a/src/libraries/System.Data.Odbc/src/Common/System/Data/Common/AdapterUtil.Odbc.cs
+++ b/src/libraries/System.Data.Odbc/src/Common/System/Data/Common/AdapterUtil.Odbc.cs
@@ -656,7 +656,6 @@ internal static int StringLength(string inputString)
             return ((null != inputString) ? inputString.Length : 0);
         }
 
-        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
         internal static IntPtr IntPtrOffset(IntPtr pbase, int offset)
         {
             if (4 == ADP.PtrSize)
diff --git a/src/libraries/System.Data.Odbc/src/Common/System/Data/ProviderBase/DbBuffer.cs b/src/libraries/System.Data.Odbc/src/Common/System/Data/ProviderBase/DbBuffer.cs
index 6fa5604bb79d3..61b550a5e6b4e 100644
--- a/src/libraries/System.Data.Odbc/src/Common/System/Data/ProviderBase/DbBuffer.cs
+++ b/src/libraries/System.Data.Odbc/src/Common/System/Data/ProviderBase/DbBuffer.cs
@@ -19,7 +19,7 @@ protected DbBuffer(int initialSize) : base(IntPtr.Zero, true)
             if (0 < initialSize)
             {
                 _bufferLength = initialSize;
-                RuntimeHelpers.PrepareConstrainedRegions();
+
                 try { }
                 finally
                 {
@@ -62,7 +62,7 @@ internal string PtrToStringUni(int offset)
 
             string value = null;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -90,7 +90,7 @@ internal string PtrToStringUni(int offset, int length)
 
             string value = null;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -116,7 +116,7 @@ internal byte ReadByte(int offset)
 
             byte value;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -149,7 +149,7 @@ internal byte[] ReadBytes(int offset, byte[] destination, int startIndex, int le
             Debug.Assert(startIndex + length <= destination.Length, "destination too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -182,7 +182,7 @@ internal char[] ReadChars(int offset, char[] destination, int startIndex, int le
             Debug.Assert(startIndex + length <= destination.Length, "destination too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -214,7 +214,7 @@ internal short ReadInt16(int offset)
 
             short value;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -241,7 +241,7 @@ internal void ReadInt16Array(int offset, short[] destination, int startIndex, in
             Debug.Assert(startIndex + length <= destination.Length, "destination too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -266,7 +266,7 @@ internal int ReadInt32(int offset)
 
             int value;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -293,7 +293,7 @@ internal void ReadInt32Array(int offset, int[] destination, int startIndex, int
             Debug.Assert(startIndex + length <= destination.Length, "destination too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -318,7 +318,7 @@ internal long ReadInt64(int offset)
 
             long value;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -344,7 +344,7 @@ internal IntPtr ReadIntPtr(int offset)
 
             IntPtr value;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -388,7 +388,7 @@ private void StructureToPtr(int offset, object structure)
             Debug.Assert(0 == offset % ADP.PtrSize, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -412,7 +412,7 @@ internal void WriteByte(int offset, byte value)
             Debug.Assert(0 == offset % 4, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -438,7 +438,7 @@ internal void WriteBytes(int offset, byte[] source, int startIndex, int length)
             Debug.Assert(startIndex + length <= source.Length, "source too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -464,7 +464,7 @@ internal void WriteCharArray(int offset, char[] source, int startIndex, int leng
             Debug.Assert(startIndex + length <= source.Length, "source too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -493,7 +493,7 @@ internal void WriteInt16(int offset, short value)
             Debug.Assert(0 == offset % 2, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -519,7 +519,7 @@ internal void WriteInt16Array(int offset, short[] source, int startIndex, int le
             Debug.Assert(startIndex + length <= source.Length, "source too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -543,7 +543,7 @@ internal void WriteInt32(int offset, int value)
             Debug.Assert(0 == offset % 4, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -569,7 +569,7 @@ internal void WriteInt32Array(int offset, int[] source, int startIndex, int leng
             Debug.Assert(startIndex + length <= source.Length, "source too small");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -593,7 +593,7 @@ internal void WriteInt64(int offset, long value)
             Debug.Assert(0 == offset % IntPtr.Size, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -617,7 +617,7 @@ internal void WriteIntPtr(int offset, IntPtr value)
             Debug.Assert(0 == offset % IntPtr.Size, "invalid alignment");
 
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -642,7 +642,7 @@ internal unsafe void WriteSingle(int offset, float value)
         internal void ZeroMemory()
         {
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs
index f12187eeed151..be558f4ac9dda 100644
--- a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs
+++ b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcCommand.cs
@@ -675,7 +675,6 @@ private OdbcDataReader ExecuteReaderObject(CommandBehavior behavior,
                 bool mustRelease = false;
                 CNativeBuffer parameterBuffer = _cmdWrapper._nativeParameterBuffer;
 
-                RuntimeHelpers.PrepareConstrainedRegions();
                 try
                 {
                     //Handle Parameters
diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcConnectionHandle.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcConnectionHandle.cs
index 1f5b81c7f78c6..6cd776f00fa2f 100644
--- a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcConnectionHandle.cs
+++ b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcConnectionHandle.cs
@@ -57,9 +57,7 @@ private ODBC32.RetCode AutoCommitOff()
 
             Debug.Assert(HandleState.Connected <= _handleState, "AutoCommitOff while in wrong state?");
 
-            // Avoid runtime injected errors in the following block.
             // must call SQLSetConnectAttrW and set _handleState
-            RuntimeHelpers.PrepareConstrainedRegions();
             try { }
             finally
             {
@@ -141,7 +139,7 @@ internal ODBC32.RetCode BeginTransaction(ref IsolationLevel isolevel)
         internal ODBC32.RetCode CompleteTransaction(short transactionOperation)
         {
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 DangerousAddRef(ref mustRelease);
@@ -157,15 +155,12 @@ internal ODBC32.RetCode CompleteTransaction(short transactionOperation)
             }
         }
 
-        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
         private ODBC32.RetCode CompleteTransaction(short transactionOperation, IntPtr handle)
         {
             // must only call this code from ReleaseHandle or DangerousAddRef region
 
             ODBC32.RetCode retcode = ODBC32.RetCode.SUCCESS;
 
-            // using ConstrainedRegions to make the native ODBC call and change the _handleState
-            RuntimeHelpers.PrepareConstrainedRegions();
             try { }
             finally
             {
@@ -195,8 +190,6 @@ private ODBC32.RetCode Connect(string connectionString)
 
             ODBC32.RetCode retcode;
 
-            // Avoid runtime injected errors in the following block.
-            RuntimeHelpers.PrepareConstrainedRegions();
             try { }
             finally
             {
diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataReader.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataReader.cs
index a8924b3900dc6..d66f5f28a6a06 100644
--- a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataReader.cs
+++ b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcDataReader.cs
@@ -2344,7 +2344,6 @@ internal int RetrieveKeyInfo(bool needkeyinfo, QualifiedTableName qualifiedTable
             bool mustRelease = false;
             Debug.Assert(buffer.Length >= 264, "Native buffer to small (_buffer.Length < 264)");
 
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 buffer.DangerousAddRef(ref mustRelease);
@@ -2530,7 +2529,6 @@ private int RetrieveKeyInfoFromStatistics(QualifiedTableName qualifiedTableName,
             bool mustRelease = false;
             Debug.Assert(buffer.Length >= 544, "Native buffer to small (_buffer.Length < 544)");
 
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 buffer.DangerousAddRef(ref mustRelease);
diff --git a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcHandle.cs b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcHandle.cs
index 8c4f34053b0ff..4936464cb100b 100644
--- a/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcHandle.cs
+++ b/src/libraries/System.Data.Odbc/src/System/Data/Odbc/OdbcHandle.cs
@@ -21,8 +21,6 @@ protected OdbcHandle(ODBC32.SQL_HANDLE handleType, OdbcHandle parentHandle) : ba
             bool mustRelease = false;
             ODBC32.RetCode retcode = ODBC32.RetCode.SUCCESS;
 
-            // using ConstrainedRegions to make the native ODBC call and AddRef the parent
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 // validate handleType
@@ -85,7 +83,7 @@ internal OdbcHandle(OdbcStatementHandle parentHandle, ODBC32.SQL_ATTR attribute)
             int cbActual;
             ODBC32.RetCode retcode;
             bool mustRelease = false;
-            RuntimeHelpers.PrepareConstrainedRegions();
+
             try
             {
                 // must addref before calling native so it won't be released just after
diff --git a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLog.cs b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLog.cs
index 70f483375b453..192047a6ad4b5 100644
--- a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLog.cs
+++ b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLog.cs
@@ -265,7 +265,6 @@ public static void CreateEventSource(EventSourceCreationData sourceData)
                 throw new ArgumentException(SR.Format(SR.ParameterTooLong, nameof(source), 254 - EventLogKey.Length));
 
             Mutex mutex = null;
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 NetFrameworkUtils.EnterMutex(eventLogMutexName, ref mutex);
@@ -371,7 +370,6 @@ public static void Delete(string logName, string machineName)
             RegistryKey eventlogkey = null;
 
             Mutex mutex = null;
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 NetFrameworkUtils.EnterMutex(eventLogMutexName, ref mutex);
@@ -442,7 +440,6 @@ public static void DeleteEventSource(string source, string machineName)
             }
 
             Mutex mutex = null;
-            RuntimeHelpers.PrepareConstrainedRegions();
             try
             {
                 NetFrameworkUtils.EnterMutex(eventLogMutexName, ref mutex);
diff --git a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogInternal.cs b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogInternal.cs
index 38ef9a53d6665..17686e5dc3624 100644
--- a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogInternal.cs
+++ b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/EventLogInternal.cs
@@ -1250,7 +1250,7 @@ private void VerifyAndCreateSource(string sourceName, string currentMachineName)
             if (!EventLog.SourceExists(sourceName, currentMachineName, true))
             {
                 Mutex mutex = null;
-                RuntimeHelpers.PrepareConstrainedRegions();
+
                 try
                 {
                     NetFrameworkUtils.EnterMutex(eventLogMutexName, ref mutex);
diff --git a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/Reader/UnsafeNativeMethods.cs b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/Reader/UnsafeNativeMethods.cs
index 82ca07bc30352..f1a5ef3955a1d 100644
--- a/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/Reader/UnsafeNativeMethods.cs
+++ b/src/libraries/System.Diagnostics.EventLog/src/System/Diagnostics/Reader/UnsafeNativeMethods.cs
@@ -459,7 +459,6 @@ internal static extern bool EvtNext(
         internal static extern bool EvtCancel(EventLogHandle handle);
 
         [DllImport(WEVTAPI)]
-        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
         internal static extern bool EvtClose(IntPtr handle);
 
         /*
diff --git a/src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/ldap/LdapSessionOptions.cs b/src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/ldap/LdapSessionOptions.cs
index fe9d7bd40da4f..39d78ed9604e3 100644
--- a/src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/ldap/LdapSessionOptions.cs
+++ b/src/libraries/System.DirectoryServices.Protocols/src/System/DirectoryServices/Protocols/ldap/LdapSessionOptions.cs
@@ -1093,7 +1093,6 @@ private static bool AddLdapHandleRef(LdapConnection ldapConnection)
             bool success = false;
             if (ldapConnection != null && ldapConnection._ldapHandle != null && !ldapConnection._ldapHandle.IsInvalid)
             {
-                RuntimeHelpers.PrepareConstrainedRegions();
                 try { }
                 finally
                 {
@@ -1108,7 +1107,6 @@ private static void ReleaseLdapHandleRef(LdapConnection ldapConnection)
         {
             if (ldapConnection != null && ldapConnection._ldapHandle != null && !ldapConnection._ldapHandle.IsInvalid)
             {
-                RuntimeHelpers.PrepareConstrainedRegions();
                 try { }
                 finally
                 {
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermission.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermission.cs
index b4b7d8511f126..7b1ebc03ec5eb 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermission.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.DirectoryServices
 {
+#pragma warning disable SYSLIB0003
+    // Conditionally marking this type as obsolete in .NET 5+ will require diverging its net5.0 build from netstandard2.0
+    // https://github.com/dotnet/runtime/issues/39413
     public sealed class DirectoryServicesPermission : ResourcePermissionBase
     {
         public DirectoryServicesPermission() { }
@@ -13,4 +16,5 @@ public DirectoryServicesPermission(PermissionState state) { }
         public DirectoryServicesPermission(DirectoryServicesPermissionAccess permissionAccess, string path) { }
         public DirectoryServicesPermissionEntryCollection PermissionEntries { get; }
     }
+#pragma warning restore SYSLIB0003
 }
diff --git a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermissionAttribute.cs b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermissionAttribute.cs
index 4c728acd35555..b4d094115b5bd 100644
--- a/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermissionAttribute.cs
+++ b/src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermissionAttribute.cs
@@ -6,6 +6,9 @@
 
 namespace System.DirectoryServices
 {
+#pragma warning disable SYSLIB0003
+    // Conditionally marking this type as obsolete in .NET 5+ will require diverging its net5.0 build from netstandard2.0
+    // https://github.com/dotnet/runtime/issues/39413
     [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct |
         AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Event,
         AllowMultiple = true, Inherited = false)]
@@ -16,4 +19,5 @@ public DirectoryServicesPermissionAttribute(SecurityAction action) : base(defaul
         public string Path { get; set; }
         public override IPermission CreatePermission() { return default(IPermission); }
     }
+#pragma warning restore SYSLIB0003
 }
diff --git a/src/libraries/System.DirectoryServices/tests/System.DirectoryServices.Tests.csproj b/src/libraries/System.DirectoryServices/tests/System.DirectoryServices.Tests.csproj
index 8cf66c642997f..53be1a5cb23a6 100644
--- a/src/libraries/System.DirectoryServices/tests/System.DirectoryServices.Tests.csproj
+++ b/src/libraries/System.DirectoryServices/tests/System.DirectoryServices.Tests.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <NoWarn>$(NoWarn);CS0618</NoWarn>
+    <!-- SYSLIB0003: CAS is obsolete, but we still have tests referencing it -->
+    <NoWarn>$(NoWarn);SYSLIB0003</NoWarn>
     <TargetFrameworks>$(NetCoreAppCurrent)-Windows_NT;$(NetFrameworkCurrent)</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Drawing.Common/src/System/Drawing/BufferedGraphicsManager.Windows.cs b/src/libraries/System.Drawing.Common/src/System/Drawing/BufferedGraphicsManager.Windows.cs
index ed5e7df462b81..5612b92e732b2 100644
--- a/src/libraries/System.Drawing.Common/src/System/Drawing/BufferedGraphicsManager.Windows.cs
+++ b/src/libraries/System.Drawing.Common/src/System/Drawing/BufferedGraphicsManager.Windows.cs
@@ -28,7 +28,6 @@ static BufferedGraphicsManager()
         /// <summary>
         /// Called on process exit
         /// </summary>
-        [PrePrepareMethod]
         private static void OnShutdown(object? sender, EventArgs e) => Current.Invalidate();
     }
 }
diff --git a/src/libraries/System.Drawing.Common/src/System/Drawing/Graphics.Windows.cs b/src/libraries/System.Drawing.Common/src/System/Drawing/Graphics.Windows.cs
index cca9e01e34319..9428febc1a763 100644
--- a/src/libraries/System.Drawing.Common/src/System/Drawing/Graphics.Windows.cs
+++ b/src/libraries/System.Drawing.Common/src/System/Drawing/Graphics.Windows.cs
@@ -918,7 +918,6 @@ public static IntPtr GetHalftonePalette()
         }
 
         // This is called from AppDomain.ProcessExit and AppDomain.DomainUnload.
-        [PrePrepareMethod]
         private static void OnDomainUnload(object? sender, EventArgs e)
         {
             if (s_halftonePalette != IntPtr.Zero)
diff --git a/src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Unix.cs b/src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Unix.cs
index b9b6e77163be0..0bafe3e36be07 100644
--- a/src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Unix.cs
+++ b/src/libraries/System.Drawing.Common/src/System/Drawing/ImageAnimator.Unix.cs
@@ -132,7 +132,9 @@ public static void StopAnimate(Image image, EventHandler onFrameChangedHandler)
             if (ht.ContainsKey(image))
             {
                 AnimateEventArgs evtArgs = (AnimateEventArgs)ht[image]!;
+#pragma warning disable SYSLIB0006 // https://github.com/dotnet/runtime/issues/39405
                 evtArgs.RunThread!.Abort();
+#pragma warning restore SYSLIB0006
                 ht.Remove(image);
             }
         }
diff --git a/src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Windows.cs b/src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Windows.cs
index 50aa16a4ecc3b..8168691c9a93f 100644
--- a/src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Windows.cs
+++ b/src/libraries/System.IO.Pipes/src/System/IO/Pipes/NamedPipeServerStream.Windows.cs
@@ -221,7 +221,17 @@ public void RunAsClient(PipeStreamImpersonationWorker impersonationWorker)
         {
             CheckWriteOperations();
             ExecuteHelper execHelper = new ExecuteHelper(impersonationWorker, InternalHandle);
-            RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(tryCode, cleanupCode, execHelper);
+            bool exceptionThrown = true;
+
+            try
+            {
+                ImpersonateAndTryCode(execHelper);
+                exceptionThrown = false;
+            }
+            finally
+            {
+                RevertImpersonationOnBackout(execHelper, exceptionThrown);
+            }
 
             // now handle win32 impersonate/revert specific errors by throwing corresponding exceptions
             if (execHelper._impersonateErrorCode != 0)
@@ -234,11 +244,6 @@ public void RunAsClient(PipeStreamImpersonationWorker impersonationWorker)
             }
         }
 
-        // the following are needed for CER
-
-        private static readonly RuntimeHelpers.TryCode tryCode = new RuntimeHelpers.TryCode(ImpersonateAndTryCode);
-        private static readonly RuntimeHelpers.CleanupCode cleanupCode = new RuntimeHelpers.CleanupCode(RevertImpersonationOnBackout);
-
         private static void ImpersonateAndTryCode(object? helper)
         {
             ExecuteHelper execHelper = (ExecuteHelper)helper!;
diff --git a/src/libraries/System.IO.Ports/tests/Support/PortsTest.cs b/src/libraries/System.IO.Ports/tests/Support/PortsTest.cs
index 56502d09496db..a1b45cc152983 100644
--- a/src/libraries/System.IO.Ports/tests/Support/PortsTest.cs
+++ b/src/libraries/System.IO.Ports/tests/Support/PortsTest.cs
@@ -37,9 +37,9 @@ public static void Fail(string format, params object[] args)
             Assert.True(false, string.Format(format, args));
         }
 
-#pragma warning disable MSLIB0001 // Encoding.UTF7 property is obsolete
+#pragma warning disable SYSLIB0001 // Encoding.UTF7 property is obsolete
         protected static Encoding LegacyUTF7Encoding => Encoding.UTF7;
-#pragma warning restore MSLIB0001
+#pragma warning restore SYSLIB0001
 
         /// <summary>
         /// Returns a value stating whether <paramref name="encoding"/> is UTF-7.
diff --git a/src/libraries/System.Linq.Expressions/ref/System.Linq.Expressions.cs b/src/libraries/System.Linq.Expressions/ref/System.Linq.Expressions.cs
index d26f21a5b2265..09923d433d67e 100644
--- a/src/libraries/System.Linq.Expressions/ref/System.Linq.Expressions.cs
+++ b/src/libraries/System.Linq.Expressions/ref/System.Linq.Expressions.cs
@@ -1144,6 +1144,7 @@ internal CallSite() { }
     public abstract partial class DebugInfoGenerator
     {
         protected DebugInfoGenerator() { }
+        [System.ObsoleteAttribute("The CreatePdbGenerator API is not supported and throws PlatformNotSupportedException.", DiagnosticId = "SYSLIB0008", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Runtime.CompilerServices.DebugInfoGenerator CreatePdbGenerator() { throw null; }
         public abstract void MarkSequencePoint(System.Linq.Expressions.LambdaExpression method, int ilOffset, System.Linq.Expressions.DebugInfoExpression sequencePoint);
     }
diff --git a/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj b/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
index c6555f3207ee8..07d0cebd1746e 100644
--- a/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
+++ b/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
@@ -11,6 +11,8 @@
     <DefineConstants Condition=" '$(FeatureInterpret)' == 'true' ">$(DefineConstants);FEATURE_INTERPRET</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="$(CommonPath)System\Obsoletions.cs"
+             Link="Common\System\Obsoletions.cs" />
     <Compile Include="$(CommonPath)System\Collections\Generic\ArrayBuilder.cs"
              Link="Common\System\Collections\Generic\ArrayBuilder.cs" />
     <Compile Include="System\Dynamic\Utils\CacheDict.cs" />
diff --git a/src/libraries/System.Linq.Expressions/src/System/Runtime/CompilerServices/DebugInfoGenerator.cs b/src/libraries/System.Linq.Expressions/src/System/Runtime/CompilerServices/DebugInfoGenerator.cs
index 5994252484795..a1bd0c8c45fc5 100644
--- a/src/libraries/System.Linq.Expressions/src/System/Runtime/CompilerServices/DebugInfoGenerator.cs
+++ b/src/libraries/System.Linq.Expressions/src/System/Runtime/CompilerServices/DebugInfoGenerator.cs
@@ -17,6 +17,7 @@ public abstract class DebugInfoGenerator
         /// Creates PDB symbol generator.
         /// </summary>
         /// <returns>PDB symbol generator.</returns>
+        [Obsolete(Obsoletions.CreatePdbGeneratorMessage, DiagnosticId = Obsoletions.CreatePdbGeneratorDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static DebugInfoGenerator CreatePdbGenerator()
         {
             // Creating PDBs is not supported in .NET Core
diff --git a/src/libraries/System.Net.Requests/ref/System.Net.Requests.cs b/src/libraries/System.Net.Requests/ref/System.Net.Requests.cs
index fcd291d8d7422..1fc5c6d2bdbb6 100644
--- a/src/libraries/System.Net.Requests/ref/System.Net.Requests.cs
+++ b/src/libraries/System.Net.Requests/ref/System.Net.Requests.cs
@@ -12,7 +12,9 @@ internal AuthenticationManager() { }
         public static System.Net.ICredentialPolicy? CredentialPolicy { get { throw null; } set { } }
         public static System.Collections.Specialized.StringDictionary CustomTargetNameDictionary { get { throw null; } }
         public static System.Collections.IEnumerator RegisteredModules { get { throw null; } }
+        [System.ObsoleteAttribute("The AuthenticationManager Authenticate and PreAuthenticate methods are not supported and throw PlatformNotSupportedException.", DiagnosticId = "SYSLIB0009", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Net.Authorization? Authenticate(string challenge, System.Net.WebRequest request, System.Net.ICredentials credentials) { throw null; }
+        [System.ObsoleteAttribute("The AuthenticationManager Authenticate and PreAuthenticate methods are not supported and throw PlatformNotSupportedException.", DiagnosticId = "SYSLIB0009", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Net.Authorization? PreAuthenticate(System.Net.WebRequest request, System.Net.ICredentials credentials) { throw null; }
         public static void Register(System.Net.IAuthenticationModule authenticationModule) { }
         public static void Unregister(System.Net.IAuthenticationModule authenticationModule) { }
diff --git a/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj b/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
index bfe01ea9e1ac4..9db098574bbd4 100644
--- a/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
+++ b/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
@@ -43,6 +43,8 @@
     <Compile Include="System\Net\Cache\HttpRequestCacheLevel.cs" />
     <Compile Include="System\Net\Cache\HttpRequestCachePolicy.cs" />
     <Compile Include="System\Net\NetEventSource.Requests.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs"
+             Link="Common\System\Obsoletions.cs" />
     <Compile Include="$(CommonPath)System\Net\Http\HttpHandlerDefaults.cs"
              Link="Common\System\Net\Http\HttpHandlerDefaults.cs" />
     <Compile Include="$(CommonPath)System\Net\InternalException.cs"
diff --git a/src/libraries/System.Net.Requests/src/System/Net/AuthenticationManager.cs b/src/libraries/System.Net.Requests/src/System/Net/AuthenticationManager.cs
index a0737c26a4130..5c01404351913 100644
--- a/src/libraries/System.Net.Requests/src/System/Net/AuthenticationManager.cs
+++ b/src/libraries/System.Net.Requests/src/System/Net/AuthenticationManager.cs
@@ -14,9 +14,11 @@ private AuthenticationManager() { }
 
         public static StringDictionary CustomTargetNameDictionary { get; } = new StringDictionary();
 
+        [Obsolete(Obsoletions.AuthenticationManagerMessage, DiagnosticId = Obsoletions.AuthenticationManagerDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static Authorization? Authenticate(string challenge, WebRequest request, ICredentials credentials) =>
             throw new PlatformNotSupportedException();
 
+        [Obsolete(Obsoletions.AuthenticationManagerMessage, DiagnosticId = Obsoletions.AuthenticationManagerDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static Authorization? PreAuthenticate(WebRequest request, ICredentials credentials) =>
             throw new PlatformNotSupportedException();
 
diff --git a/src/libraries/System.Net.Requests/tests/AuthenticationManagerTest.cs b/src/libraries/System.Net.Requests/tests/AuthenticationManagerTest.cs
index fab7e11174206..0d08bbe9b9744 100644
--- a/src/libraries/System.Net.Requests/tests/AuthenticationManagerTest.cs
+++ b/src/libraries/System.Net.Requests/tests/AuthenticationManagerTest.cs
@@ -14,8 +14,10 @@ public class AuthenticationManagerTest
         [Fact]
         public void Authenticate_NotSupported()
         {
+#pragma warning disable SYSLIB0009 // The methods are obsolete
             Assert.Throws<PlatformNotSupportedException>(() => AuthenticationManager.Authenticate(null, null, null));
             Assert.Throws<PlatformNotSupportedException>(() => AuthenticationManager.PreAuthenticate(null, null));
+#pragma warning restore SYSLIB0009
         }
 
         [Fact]
diff --git a/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems b/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
index 63314c0e85b91..b217b4289df66 100644
--- a/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
+++ b/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
@@ -461,7 +461,6 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Object.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\ObjectDisposedException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\ObsoleteAttribute.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)System\Obsoletions.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\OperatingSystem.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\OperationCanceledException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\OutOfMemoryException.cs" />
@@ -1105,6 +1104,9 @@
     <Compile Include="$(CommonPath)System\HResults.cs">
       <Link>Common\System\HResults.cs</Link>
     </Compile>
+    <Compile Include="$(CommonPath)System\Obsoletions.cs">
+      <Link>Common\System\Obsoletions.cs</Link>
+    </Compile>
     <Compile Include="$(CommonPath)System\SR.cs">
       <Link>Common\System\SR.cs</Link>
     </Compile>
diff --git a/src/libraries/System.Private.CoreLib/src/System/AppDomain.cs b/src/libraries/System.Private.CoreLib/src/System/AppDomain.cs
index 696e1f439494c..06c64105edd09 100644
--- a/src/libraries/System.Private.CoreLib/src/System/AppDomain.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/AppDomain.cs
@@ -36,6 +36,7 @@ private AppDomain() { }
 
         public AppDomainSetup SetupInformation => new AppDomainSetup();
 
+        [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public PermissionSet PermissionSet => new PermissionSet(PermissionState.Unrestricted);
 
         public event UnhandledExceptionEventHandler? UnhandledException
diff --git a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs
index 88a677be875c0..cabafa707239e 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/TraceLogging/TraceLoggingEventSource.cs
@@ -440,7 +440,7 @@ private unsafe void WriteMultiMergeInner(
                 descriptors[1].SetMetadata(pMetadata1, nameInfo.nameMetadata.Length, 1);
                 descriptors[2].SetMetadata(pMetadata2, eventTypes.typeMetadata.Length, 1);
 
-#if (!ES_BUILD_PCL)
+#if (!ES_BUILD_PCL && !NETCOREAPP)
                 System.Runtime.CompilerServices.RuntimeHelpers.PrepareConstrainedRegions();
 #endif
                 try
@@ -624,7 +624,7 @@ private unsafe void WriteImpl(
                         descriptors[2].SetMetadata(pMetadata2, eventTypes.typeMetadata.Length, 1);
 #endif // FEATURE_MANAGED_ETW
 
-#if (!ES_BUILD_PCL)
+#if (!ES_BUILD_PCL && !NETCOREAPP)
                         System.Runtime.CompilerServices.RuntimeHelpers.PrepareConstrainedRegions();
 #endif
                         EventOpcode opcode = (EventOpcode)descriptor.Opcode;
@@ -731,7 +731,7 @@ private unsafe void WriteToAllListeners(string? eventName, ref EventDescriptor e
             DispatchToAllListeners(-1, eventCallbackArgs);
         }
 
-#if (!ES_BUILD_PCL)
+#if (!ES_BUILD_PCL && !NETCOREAPP)
         [System.Runtime.ConstrainedExecution.ReliabilityContract(
             System.Runtime.ConstrainedExecution.Consistency.WillNotCorruptState,
             System.Runtime.ConstrainedExecution.Cer.Success)]
diff --git a/src/libraries/System.Private.CoreLib/src/System/MarshalByRefObject.cs b/src/libraries/System.Private.CoreLib/src/System/MarshalByRefObject.cs
index 25da5a6ac0a2b..042617e4ba08c 100644
--- a/src/libraries/System.Private.CoreLib/src/System/MarshalByRefObject.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/MarshalByRefObject.cs
@@ -13,11 +13,13 @@ protected MarshalByRefObject()
         {
         }
 
+        [Obsolete(Obsoletions.RemotingApisMessage, DiagnosticId = Obsoletions.RemotingApisDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public object GetLifetimeService()
         {
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_Remoting);
         }
 
+        [Obsolete(Obsoletions.RemotingApisMessage, DiagnosticId = Obsoletions.RemotingApisDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public virtual object InitializeLifetimeService()
         {
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_Remoting);
diff --git a/src/libraries/System.Private.CoreLib/src/System/Obsoletions.cs b/src/libraries/System.Private.CoreLib/src/System/Obsoletions.cs
deleted file mode 100644
index ce8f37465a463..0000000000000
--- a/src/libraries/System.Private.CoreLib/src/System/Obsoletions.cs
+++ /dev/null
@@ -1,13 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-namespace System
-{
-    internal static class Obsoletions
-    {
-        internal const string SharedUrlFormat = "https://aka.ms/dotnet-warnings/{0}";
-
-        internal const string SystemTextEncodingUTF7Message = "The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.";
-        internal const string SystemTextEncodingUTF7DiagId = "MSLIB0001";
-    }
-}
diff --git a/src/libraries/System.Private.CoreLib/src/System/Reflection/Assembly.cs b/src/libraries/System.Private.CoreLib/src/System/Reflection/Assembly.cs
index e0b1cab0648e0..bd6dd45fb0b45 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Reflection/Assembly.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Reflection/Assembly.cs
@@ -165,6 +165,7 @@ public override string ToString()
         /*
           Returns true if the assembly was loaded from the global assembly cache.
         */
+        [Obsolete(Obsoletions.GlobalAssemblyCacheMessage, DiagnosticId = Obsoletions.GlobalAssemblyCacheDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public virtual bool GlobalAssemblyCache => throw NotImplemented.ByDesign;
         public virtual long HostContext => throw NotImplemented.ByDesign;
 
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs
index 083b6a1ed18c4..727a1bee1a359 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs
@@ -88,6 +88,7 @@ public static object GetUninitializedObject(
             return GetUninitializedObjectInternal(type);
         }
 
+        [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static void ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, object? userData)
         {
             if (code == null)
@@ -108,18 +109,22 @@ public static void ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode ba
             }
         }
 
+        [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static void PrepareContractedDelegate(Delegate d)
         {
         }
 
+        [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static void ProbeForSufficientStack()
         {
         }
 
+        [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static void PrepareConstrainedRegions()
         {
         }
 
+        [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static void PrepareConstrainedRegionsNoOP()
         {
         }
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Cer.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Cer.cs
index e15003a9162c3..40dbd4fa2a228 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Cer.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Cer.cs
@@ -3,6 +3,7 @@
 
 namespace System.Runtime.ConstrainedExecution
 {
+    [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     public enum Cer : int
     {
         None = 0,
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Consistency.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Consistency.cs
index a22f4b2d20c90..12f3e8aa76374 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Consistency.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/Consistency.cs
@@ -3,6 +3,7 @@
 
 namespace System.Runtime.ConstrainedExecution
 {
+    [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     public enum Consistency : int
     {
         MayCorruptProcess = 0,
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/PrePrepareMethodAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/PrePrepareMethodAttribute.cs
index c8c3ecf4b5955..e0eb0c79a6b10 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/PrePrepareMethodAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/PrePrepareMethodAttribute.cs
@@ -3,6 +3,7 @@
 
 namespace System.Runtime.ConstrainedExecution
 {
+    [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage(AttributeTargets.Constructor | AttributeTargets.Method, Inherited = false)]
     public sealed class PrePrepareMethodAttribute : Attribute
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs
index 261b3de78e31e..d9a8272fbb78d 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/ConstrainedExecution/ReliabilityContractAttribute.cs
@@ -17,6 +17,7 @@
 
 namespace System.Runtime.ConstrainedExecution
 {
+    [Obsolete(Obsoletions.ConstrainedExecutionRegionMessage, DiagnosticId = Obsoletions.ConstrainedExecutionRegionDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Interface /* | AttributeTargets.Delegate*/, Inherited = false)]
     public sealed class ReliabilityContractAttribute : Attribute
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/IPermission.cs b/src/libraries/System.Private.CoreLib/src/System/Security/IPermission.cs
index 500b0371b470e..6ed3a924f0420 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/IPermission.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/IPermission.cs
@@ -3,6 +3,7 @@
 
 namespace System.Security
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     public partial interface IPermission : ISecurityEncodable
     {
         IPermission Copy();
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/IStackWalk.cs b/src/libraries/System.Private.CoreLib/src/System/Security/IStackWalk.cs
index 3f2e81469049a..cd0a5ac1f7d6b 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/IStackWalk.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/IStackWalk.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security
 {
+#if SYSTEM_PRIVATE_CORELIB
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public partial interface IStackWalk
     {
         void Assert();
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/PermissionSet.cs b/src/libraries/System.Private.CoreLib/src/System/Security/PermissionSet.cs
index a3d4a8b49b172..b64def0d28d80 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/PermissionSet.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/PermissionSet.cs
@@ -8,6 +8,9 @@
 
 namespace System.Security
 {
+#if SYSTEM_PRIVATE_CORELIB
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public partial class PermissionSet : ICollection, IEnumerable, IDeserializationCallback, ISecurityEncodable, IStackWalk
     {
         public PermissionSet(PermissionState state) { }
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/CodeAccessSecurityAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/CodeAccessSecurityAttribute.cs
index 6504fc5ad787e..742b076e33089 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/CodeAccessSecurityAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/CodeAccessSecurityAttribute.cs
@@ -3,6 +3,7 @@
 
 namespace System.Security.Permissions
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public abstract partial class CodeAccessSecurityAttribute : SecurityAttribute
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/PermissionState.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/PermissionState.cs
index abcc0a95fff40..87c4bb40a1dba 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/PermissionState.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/PermissionState.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if SYSTEM_PRIVATE_CORELIB
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum PermissionState
     {
         None = 0,
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAction.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAction.cs
index 17242e2d8a27e..6bbaa15915f30 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAction.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAction.cs
@@ -3,20 +3,17 @@
 
 namespace System.Security.Permissions
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     public enum SecurityAction
     {
         Assert = 3,
         Demand = 2,
-        [Obsolete("Deny is obsolete and will be removed in a future release of the .NET Framework. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         Deny = 4,
         InheritanceDemand = 7,
         LinkDemand = 6,
         PermitOnly = 5,
-        [Obsolete("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestMinimum = 8,
-        [Obsolete("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestOptional = 9,
-        [Obsolete("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestRefuse = 10,
     }
 }
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAttribute.cs
index 0607153928345..7bd47050ff5a1 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityAttribute.cs
@@ -3,6 +3,7 @@
 
 namespace System.Security.Permissions
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public abstract partial class SecurityAttribute : Attribute
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionAttribute.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionAttribute.cs
index 4d2b672ee59a8..1c038c0ec46d7 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionAttribute.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionAttribute.cs
@@ -3,6 +3,7 @@
 
 namespace System.Security.Permissions
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class SecurityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionFlag.cs b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionFlag.cs
index 07700b2f86199..5202a9d3d6eb5 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionFlag.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Security/Permissions/SecurityPermissionFlag.cs
@@ -3,6 +3,7 @@
 
 namespace System.Security.Permissions
 {
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [Flags]
     public enum SecurityPermissionFlag
     {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs b/src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs
index c1452204b906e..6bedf38c786a2 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Text/Encoding.cs
@@ -245,9 +245,9 @@ public static Encoding GetEncoding(int codepage)
 
                         if (LocalAppContextSwitches.EnableUnsafeUTF7Encoding)
                         {
-#pragma warning disable MSLIB0001 // Encoding.UTF7 property getter is obsolete
+#pragma warning disable SYSLIB0001 // Encoding.UTF7 property getter is obsolete
                             return UTF7;
-#pragma warning restore MSLIB0001
+#pragma warning restore SYSLIB0001
                         }
                         else
                         {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Text/UTF7Encoding.cs b/src/libraries/System.Private.CoreLib/src/System/Text/UTF7Encoding.cs
index fb6cbbb889365..7b416f1b4b4a9 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Text/UTF7Encoding.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Text/UTF7Encoding.cs
@@ -26,11 +26,11 @@ public class UTF7Encoding : Encoding
         private const string optionalChars =
             "!\"#$%&*;<=>@[]^_`{|}";
 
-#pragma warning disable MSLIB0001
+#pragma warning disable SYSLIB0001
         // Used by Encoding.UTF7 for lazy initialization
         // The initialization code will not be run until a static member of the class is referenced
         internal static readonly UTF7Encoding s_default = new UTF7Encoding();
-#pragma warning restore MSLIB0001
+#pragma warning restore SYSLIB0001
 
         // The set of base 64 characters.
         private byte[] _base64Bytes;
diff --git a/src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs b/src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs
index edc05663a0449..f468e6cab13a8 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Threading/Thread.cs
@@ -177,11 +177,13 @@ public string? Name
             }
         }
 
+        [Obsolete(Obsoletions.ThreadAbortMessage, DiagnosticId = Obsoletions.ThreadAbortDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void Abort()
         {
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_ThreadAbort);
         }
 
+        [Obsolete(Obsoletions.ThreadAbortMessage, DiagnosticId = Obsoletions.ThreadAbortDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void Abort(object? stateInfo)
         {
             throw new PlatformNotSupportedException(SR.PlatformNotSupported_ThreadAbort);
diff --git a/src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compilation.cs b/src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compilation.cs
index 3ebebfb002a8b..fe7d84f63bd4b 100644
--- a/src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compilation.cs
+++ b/src/libraries/System.Private.Xml/src/System/Xml/Serialization/Compilation.cs
@@ -301,10 +301,7 @@ internal static bool GenerateSerializerToStream(XmlMapping[] xmlMappings, Type[]
                             continue;
                         }
 
-                        if (!a.GlobalAssemblyCache)
-                        {
-                            assemblies[name] = a;
-                        }
+                        assemblies[name] = a;
                     }
                 }
 
diff --git a/src/libraries/System.Reflection.Emit/ref/System.Reflection.Emit.cs b/src/libraries/System.Reflection.Emit/ref/System.Reflection.Emit.cs
index 47190abe5bfbe..bd34fa007dcee 100644
--- a/src/libraries/System.Reflection.Emit/ref/System.Reflection.Emit.cs
+++ b/src/libraries/System.Reflection.Emit/ref/System.Reflection.Emit.cs
@@ -12,6 +12,7 @@ internal AssemblyBuilder() { }
         public override string? CodeBase { get { throw null; } }
         public override System.Reflection.MethodInfo? EntryPoint { get { throw null; } }
         public override string? FullName { get { throw null; } }
+        [Obsolete("The Global Assembly Cache is not supported.", DiagnosticId = "SYSLIB0005", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public override bool GlobalAssemblyCache { get { throw null; } }
         public override long HostContext { get { throw null; } }
         public override string ImageRuntimeVersion { get { throw null; } }
diff --git a/src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj b/src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj
index bb96d4ba71e6b..80692bdfc3a8a 100644
--- a/src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj
+++ b/src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj
@@ -8,8 +8,10 @@
     <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
     <Nullable>enable</Nullable>
   </PropertyGroup>
-    <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
+  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
+    <!-- Constrained Execution Regions only apply to netstandard2.0 and net4* -->
+    <DefineConstants Condition="$(TargetFramework.StartsWith('netstandard2.0')) or $(TargetFramework.StartsWith('net4'))">$(DefineConstants);FEATURE_CER</DefineConstants>
     <PackageTargetFramework Condition="'$(TargetFramework)' == 'netstandard1.1'">netstandard1.1;portable-net45+win8</PackageTargetFramework>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/MemoryMappedFileBlock.cs b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/MemoryMappedFileBlock.cs
index 899fdee68db30..37b3dc6e4da23 100644
--- a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/MemoryMappedFileBlock.cs
+++ b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/MemoryMappedFileBlock.cs
@@ -17,14 +17,13 @@ private sealed class DisposableData : CriticalDisposableObject
 
             public DisposableData(IDisposable accessor, SafeBuffer safeBuffer, long offset)
             {
+#if FEATURE_CER
                 // Make sure the current thread isn't aborted in between acquiring the pointer and assigning the fields.
-#if !NETSTANDARD1_1
                 RuntimeHelpers.PrepareConstrainedRegions();
-#endif
                 try
-                {
-                }
+                { /* intentionally left blank */ }
                 finally
+#endif
                 {
                     byte* basePointer = null;
                     safeBuffer.AcquirePointer(ref basePointer);
@@ -37,15 +36,14 @@ public DisposableData(IDisposable accessor, SafeBuffer safeBuffer, long offset)
 
             protected override void Release()
             {
+#if FEATURE_CER
                 // Make sure the current thread isn't aborted in between zeroing the references and releasing/disposing.
                 // Safe buffer only frees the underlying resource if its ref count drops to zero, so we have to make sure it does.
-#if !NETSTANDARD1_1
                 RuntimeHelpers.PrepareConstrainedRegions();
-#endif
                 try
-                {
-                }
+                { /* intentionally left blank */ }
                 finally
+#endif
                 {
                     Interlocked.Exchange(ref _safeBuffer, null)?.ReleasePointer();
                     Interlocked.Exchange(ref _accessor, null)?.Dispose();
diff --git a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/NativeHeapMemoryBlock.cs b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/NativeHeapMemoryBlock.cs
index ec1c4579d25eb..552a854b0a51a 100644
--- a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/NativeHeapMemoryBlock.cs
+++ b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/MemoryBlocks/NativeHeapMemoryBlock.cs
@@ -21,14 +21,13 @@ private unsafe sealed class DisposableData : CriticalDisposableObject
 
             public DisposableData(int size)
             {
+#if FEATURE_CER
                 // make sure the current thread isn't aborted in between allocating and storing the pointer
-#if !NETSTANDARD1_1
                 RuntimeHelpers.PrepareConstrainedRegions();
-#endif
                 try
-                {
-                }
+                { /* intentionally left blank */ }
                 finally
+#endif
                 {
                     _pointer = Marshal.AllocHGlobal(size);
                 }
@@ -36,14 +35,13 @@ public DisposableData(int size)
 
             protected override void Release()
             {
+#if FEATURE_CER
                 // make sure the current thread isn't aborted in between zeroing the pointer and freeing the memory
-#if !NETSTANDARD1_1
                 RuntimeHelpers.PrepareConstrainedRegions();
-#endif
                 try
-                {
-                }
+                { /* intentionally left blank */ }
                 finally
+#endif
                 {
                     IntPtr ptr = Interlocked.Exchange(ref _pointer, IntPtr.Zero);
                     if (ptr != IntPtr.Zero)
diff --git a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/PinnedObject.cs b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/PinnedObject.cs
index 8ee38c050239c..a2dfc0ff31b68 100644
--- a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/PinnedObject.cs
+++ b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Internal/Utilities/PinnedObject.cs
@@ -17,14 +17,13 @@ internal sealed class PinnedObject : CriticalDisposableObject
 
         public PinnedObject(object obj)
         {
+#if FEATURE_CER
             // Make sure the current thread isn't aborted in between allocating the handle and storing it.
-#if !NETSTANDARD1_1
             RuntimeHelpers.PrepareConstrainedRegions();
-#endif
             try
-            {
-            }
+            { /* intentionally left blank */ }
             finally
+#endif
             {
                 _handle = GCHandle.Alloc(obj, GCHandleType.Pinned);
                 _isValid = 1;
@@ -33,8 +32,8 @@ public PinnedObject(object obj)
 
         protected override void Release()
         {
+#if FEATURE_CER
             // Make sure the current thread isn't aborted in between zeroing the handle and freeing it.
-#if !NETSTANDARD1_1
             RuntimeHelpers.PrepareConstrainedRegions();
 #endif
             try
diff --git a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/Internal/VirtualHeap.cs b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/Internal/VirtualHeap.cs
index 3de6b68667782..551ee9112c964 100644
--- a/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/Internal/VirtualHeap.cs
+++ b/src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/Internal/VirtualHeap.cs
@@ -45,14 +45,13 @@ private VirtualHeap()
 
         protected override void Release()
         {
+#if FEATURE_CER
             // Make sure the current thread isn't aborted in the middle of the operation.
-#if !NETSTANDARD1_1
             RuntimeHelpers.PrepareConstrainedRegions();
-#endif
             try
-            {
-            }
+            { /* intentionally left blank */ }
             finally
+#endif
             {
                 var blobs = Interlocked.Exchange(ref _blobs, null);
 
@@ -94,13 +93,12 @@ internal MemoryBlock AddBlob(uint rawHandle, byte[] value)
             var blobs = GetBlobs();
 
             MemoryBlock result;
-#if !NETSTANDARD1_1
+#if FEATURE_CER
             RuntimeHelpers.PrepareConstrainedRegions();
-#endif
             try
-            {
-            }
+            { /* intentionally left blank */ }
             finally
+#endif
             {
                 var blob = new PinnedBlob(GCHandle.Alloc(value, GCHandleType.Pinned), value.Length);
                 blobs.Add(rawHandle, blob);
diff --git a/src/libraries/System.Reflection.MetadataLoadContext/src/System.Reflection.MetadataLoadContext.csproj b/src/libraries/System.Reflection.MetadataLoadContext/src/System.Reflection.MetadataLoadContext.csproj
index b1f6f31cb00be..006e205f072b6 100644
--- a/src/libraries/System.Reflection.MetadataLoadContext/src/System.Reflection.MetadataLoadContext.csproj
+++ b/src/libraries/System.Reflection.MetadataLoadContext/src/System.Reflection.MetadataLoadContext.csproj
@@ -8,6 +8,10 @@
     <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
     <Nullable>enable</Nullable>
   </PropertyGroup>
+  <!-- We conditionally apply net5.0+ obsoletions -->
+  <PropertyGroup Condition="!($(TargetFramework.StartsWith('netcoreapp')) or $(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net4')))">
+    <DefineConstants>$(DefineConstants);NET50_OBSOLETIONS</DefineConstants>
+  </PropertyGroup>
   <ItemGroup>
     <Compile Include="System\CoreRtBridge.cs" />
     <Compile Include="System\Reflection\DefaultBinder.cs" />
diff --git a/src/libraries/System.Reflection.MetadataLoadContext/src/System/Reflection/TypeLoading/Assemblies/RoAssembly.cs b/src/libraries/System.Reflection.MetadataLoadContext/src/System/Reflection/TypeLoading/Assemblies/RoAssembly.cs
index 8a539e82047ab..b15e44645def2 100644
--- a/src/libraries/System.Reflection.MetadataLoadContext/src/System/Reflection/TypeLoading/Assemblies/RoAssembly.cs
+++ b/src/libraries/System.Reflection.MetadataLoadContext/src/System/Reflection/TypeLoading/Assemblies/RoAssembly.cs
@@ -145,6 +145,9 @@ public sealed override AssemblyName[] GetReferencedAssemblies()
 
         // Miscellaneous properties
         public sealed override bool ReflectionOnly => true;
+#if NET50_OBSOLETIONS
+        [Obsolete("The Global Assembly Cache is not supported.", DiagnosticId = "SYSLIB0005", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public sealed override bool GlobalAssemblyCache => false;
         public sealed override long HostContext => 0;
         public abstract override string ImageRuntimeVersion { get; }
diff --git a/src/libraries/System.Reflection.MetadataLoadContext/tests/System.Reflection.MetadataLoadContext.Tests.csproj b/src/libraries/System.Reflection.MetadataLoadContext/tests/System.Reflection.MetadataLoadContext.Tests.csproj
index 2c3eb7011daa8..be8b471a6eca9 100644
--- a/src/libraries/System.Reflection.MetadataLoadContext/tests/System.Reflection.MetadataLoadContext.Tests.csproj
+++ b/src/libraries/System.Reflection.MetadataLoadContext/tests/System.Reflection.MetadataLoadContext.Tests.csproj
@@ -2,6 +2,8 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetFrameworkCurrent)</TargetFrameworks>
+    <!-- The GAC is obsolete, but there are unit tests still referencing it -->
+    <NoWarn>$(NoWarn);SYSLIB0005</NoWarn>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="$(CommonTestPath)System\IO\TempDirectory.cs"
diff --git a/src/libraries/System.Reflection/tests/AssemblyTests.cs b/src/libraries/System.Reflection/tests/AssemblyTests.cs
index 2d39889f46681..a244bbb422248 100644
--- a/src/libraries/System.Reflection/tests/AssemblyTests.cs
+++ b/src/libraries/System.Reflection/tests/AssemblyTests.cs
@@ -229,11 +229,13 @@ public void GetType_DefaultsToItself()
             Assert.Equal(typeof(G<G<int>>), t);
         }
 
+#pragma warning disable SYSLIB0005 // Obsolete: GAC
         [Fact]
         public void GlobalAssemblyCache()
         {
             Assert.False(typeof(AssemblyTests).Assembly.GlobalAssemblyCache);
         }
+#pragma warning restore SYSLIB0005 // Obsolete: GAC
 
         [Fact]
         public void HostContext()
diff --git a/src/libraries/System.Runtime.Extensions/ref/System.Runtime.Extensions.Forwards.cs b/src/libraries/System.Runtime.Extensions/ref/System.Runtime.Extensions.Forwards.cs
index 62e356fe6ad6c..c6e0bfcc91e27 100644
--- a/src/libraries/System.Runtime.Extensions/ref/System.Runtime.Extensions.Forwards.cs
+++ b/src/libraries/System.Runtime.Extensions/ref/System.Runtime.Extensions.Forwards.cs
@@ -4,6 +4,8 @@
 // Changes to this file must follow the https://aka.ms/api-review process.
 // ------------------------------------------------------------------------------
 
+#pragma warning disable SYSLIB0003 // CAS Obsoletions
+
 [assembly:System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.AppDomain))]
 [assembly:System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.AppDomainSetup))]
 [assembly:System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.AppDomainUnloadedException))]
diff --git a/src/libraries/System.Runtime.Extensions/tests/System/AppDomainTests.cs b/src/libraries/System.Runtime.Extensions/tests/System/AppDomainTests.cs
index 89ec53ebd419b..438816856c8df 100644
--- a/src/libraries/System.Runtime.Extensions/tests/System/AppDomainTests.cs
+++ b/src/libraries/System.Runtime.Extensions/tests/System/AppDomainTests.cs
@@ -740,9 +740,11 @@ public void GetSetupInformation()
         [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         public static void GetPermissionSet()
         {
+#pragma warning disable SYSLIB0003 // Obsolete: CAS
             RemoteExecutor.Invoke(() => {
                 Assert.Equal(new PermissionSet(PermissionState.Unrestricted), AppDomain.CurrentDomain.PermissionSet);
             }).Dispose();
+#pragma warning restore SYSLIB0003 // Obsolete: CAS
         }
 
         [Theory]
diff --git a/src/libraries/System.Runtime.Extensions/tests/System/MarshalByRefObjectTest.cs b/src/libraries/System.Runtime.Extensions/tests/System/MarshalByRefObjectTest.cs
index 97c7539f80656..37f4fd1934186 100644
--- a/src/libraries/System.Runtime.Extensions/tests/System/MarshalByRefObjectTest.cs
+++ b/src/libraries/System.Runtime.Extensions/tests/System/MarshalByRefObjectTest.cs
@@ -14,8 +14,10 @@ public  class MarshalByRefObjectTest : MarshalByRefObject
         public static void MarshalByRefObjectTests()
         {
             var obj = new MarshalByRefObjectTest();
+#pragma warning disable SYSLIB0010 // Obsolete: Remoting APIs
             Assert.Throws<PlatformNotSupportedException>(() => obj.GetLifetimeService());
             Assert.Throws<PlatformNotSupportedException>(() => obj.InitializeLifetimeService());
+#pragma warning restore SYSLIB0010 // Obsolete: Remoting APIs
 
             var clone = obj.MemberwiseClone(false);
             Assert.NotNull(clone);
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/ref/System.Runtime.Serialization.Formatters.cs b/src/libraries/System.Runtime.Serialization.Formatters/ref/System.Runtime.Serialization.Formatters.cs
index 4681ba9721b76..dc9d5f71b9f3b 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/ref/System.Runtime.Serialization.Formatters.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/ref/System.Runtime.Serialization.Formatters.cs
@@ -15,11 +15,11 @@ protected Formatter() { }
         public abstract System.Runtime.Serialization.SerializationBinder? Binder { get; set; }
         public abstract System.Runtime.Serialization.StreamingContext Context { get; set; }
         public abstract System.Runtime.Serialization.ISurrogateSelector? SurrogateSelector { get; set; }
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public abstract object Deserialize(System.IO.Stream serializationStream);
         protected virtual object? GetNext(out long objID) { throw null; }
         protected virtual long Schedule(object? obj) { throw null; }
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public abstract void Serialize(System.IO.Stream serializationStream, object graph);
         protected abstract void WriteArray(object obj, string name, System.Type memberType);
         protected abstract void WriteBoolean(bool val, string name);
@@ -87,9 +87,9 @@ public partial interface IFormatter
         System.Runtime.Serialization.SerializationBinder? Binder { get; set; }
         System.Runtime.Serialization.StreamingContext Context { get; set; }
         System.Runtime.Serialization.ISurrogateSelector? SurrogateSelector { get; set; }
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         object Deserialize(System.IO.Stream serializationStream);
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         void Serialize(System.IO.Stream serializationStream, object graph);
     }
     public partial interface ISerializationSurrogate
@@ -183,9 +183,9 @@ public BinaryFormatter(System.Runtime.Serialization.ISurrogateSelector? selector
         public System.Runtime.Serialization.Formatters.TypeFilterLevel FilterLevel { get { throw null; } set { } }
         public System.Runtime.Serialization.ISurrogateSelector? SurrogateSelector { get { throw null; } set { } }
         public System.Runtime.Serialization.Formatters.FormatterTypeStyle TypeFormat { get { throw null; } set { } }
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public object Deserialize(System.IO.Stream serializationStream) { throw null; }
-        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "MSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.", DiagnosticId = "SYSLIB0011", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public void Serialize(System.IO.Stream serializationStream, object graph) { }
     }
 }
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj b/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
index 9d66e0135880a..6dd50fdba5e24 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
@@ -30,7 +30,6 @@
     <Compile Include="System\Runtime\Serialization\MemberHolder.cs" />
     <Compile Include="System\Runtime\Serialization\ObjectIDGenerator.cs" />
     <Compile Include="System\Runtime\Serialization\ObjectManager.cs" />
-    <Compile Include="System\Runtime\Serialization\Obsoletions.cs" />
     <Compile Include="System\Runtime\Serialization\SerializationBinder.cs" />
     <Compile Include="System\Runtime\Serialization\SerializationEventsCache.cs" />
     <Compile Include="System\Runtime\Serialization\SerializationFieldInfo.cs" />
@@ -70,6 +69,8 @@
     <Compile Include="System\Runtime\Serialization\Formatters\Binary\BinaryObjectWriter.cs" />
     <Compile Include="System\Runtime\Serialization\Formatters\Binary\BinaryParser.cs" />
     <Compile Include="System\Runtime\Serialization\Formatters\Binary\BinaryUtilClasses.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs"
+             Link="Common\System\Obsoletions.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Collections\HashHelpers.cs"
              Link="Common\System\Collections\HashHelpers.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatter.cs b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatter.cs
index 1fa2c68d14bcc..5d97328d8569d 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatter.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatter.cs
@@ -20,7 +20,7 @@ protected Formatter()
             m_idGenerator = new ObjectIDGenerator();
         }
 
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public abstract object Deserialize(Stream serializationStream);
 
         protected virtual object? GetNext(out long objID)
@@ -60,7 +60,7 @@ protected virtual long Schedule(object? obj)
             return id;
         }
 
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public abstract void Serialize(Stream serializationStream, object graph);
 
         protected abstract void WriteArray(object obj, string name, Type memberType);
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.Core.cs b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.Core.cs
index 9183902f0d608..95f281f633978 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.Core.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.Core.cs
@@ -7,7 +7,7 @@ namespace System.Runtime.Serialization.Formatters.Binary
 {
     public sealed partial class BinaryFormatter : IFormatter
     {
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public object Deserialize(Stream serializationStream)
         {
             // don't refactor the 'throw' into a helper method; linker will have difficulty trimming
@@ -52,7 +52,7 @@ public object Deserialize(Stream serializationStream)
             }
         }
 
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void Serialize(Stream serializationStream, object graph)
         {
             // don't refactor the 'throw' into a helper method; linker will have difficulty trimming
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.PlatformNotSupported.cs b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.PlatformNotSupported.cs
index 0a8bdd510a012..4d56deea06faf 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.PlatformNotSupported.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Formatters/Binary/BinaryFormatter.PlatformNotSupported.cs
@@ -7,11 +7,11 @@ namespace System.Runtime.Serialization.Formatters.Binary
 {
     public sealed partial class BinaryFormatter : IFormatter
     {
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public object Deserialize(Stream serializationStream)
             => throw new PlatformNotSupportedException(SR.BinaryFormatter_SerializationDisallowed);
 
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public void Serialize(Stream serializationStream, object graph)
             => throw new PlatformNotSupportedException(SR.BinaryFormatter_SerializationDisallowed);
     }
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/IFormatter.cs b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/IFormatter.cs
index 7fd7f9e3d478a..2d3e412fbfaca 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/IFormatter.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/IFormatter.cs
@@ -7,9 +7,9 @@ namespace System.Runtime.Serialization
 {
     public interface IFormatter
     {
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         object Deserialize(Stream serializationStream);
-        [Obsolete(Obsoletions.InsecureSerializationMessage, DiagnosticId = Obsoletions.InsecureSerializationDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+        [Obsolete(Obsoletions.BinaryFormatterMessage, DiagnosticId = Obsoletions.BinaryFormatterDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         void Serialize(Stream serializationStream, object graph);
         ISurrogateSelector? SurrogateSelector { get; set; }
         SerializationBinder? Binder { get; set; }
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Obsoletions.cs b/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Obsoletions.cs
deleted file mode 100644
index 191d0fa071d99..0000000000000
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System/Runtime/Serialization/Obsoletions.cs
+++ /dev/null
@@ -1,13 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-
-namespace System.Runtime.Serialization
-{
-    internal static class Obsoletions
-    {
-        internal const string SharedUrlFormat = "https://aka.ms/dotnet-warnings/{0}";
-
-        internal const string InsecureSerializationMessage = "BinaryFormatter serialization is obsolete and should not be used. See https://aka.ms/binaryformatter for more information.";
-        internal const string InsecureSerializationDiagId = "MSLIB0003";
-    }
-}
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/tests/BinaryFormatterTestData.cs b/src/libraries/System.Runtime.Serialization.Formatters/tests/BinaryFormatterTestData.cs
index 6e3a44df40f4e..3e9099231db18 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/tests/BinaryFormatterTestData.cs
+++ b/src/libraries/System.Runtime.Serialization.Formatters/tests/BinaryFormatterTestData.cs
@@ -412,11 +412,13 @@ public static IEnumerable<object[]> SerializableObjects()
             var formatException = new FormatException("message", exception);
             yield return new object[] { PopulateException(formatException), new TypeSerializableValue[] { new TypeSerializableValue("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", TargetFrameworkMoniker.netcoreapp20), new TypeSerializableValue("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", TargetFrameworkMoniker.netfx461) } };
 
+#pragma warning disable SYSLIB0003 // Obsolete: CAS
             var hostProtectionException = new HostProtectionException("message", exception);
             yield return new object[] { PopulateException(hostProtectionException), new TypeSerializableValue[] { new TypeSerializableValue("AAEAAAD/////AQAAAAAAAAAEAQAAACdTeXN0ZW0uU2VjdXJpdHkuSG9zdFByb3RlY3Rpb25FeGNlcHRpb24OAAAACUNsYXNzTmFtZQdNZXNzYWdlBERhdGEOSW5uZXJFeGNlcHRpb24HSGVscFVSTBBTdGFja1RyYWNlU3RyaW5nFlJlbW90ZVN0YWNrVHJhY2VTdHJpbmcQUmVtb3RlU3RhY2tJbmRleA9FeGNlcHRpb25NZXRob2QHSFJlc3VsdAZTb3VyY2UNV2F0c29uQnVja2V0cxJQcm90ZWN0ZWRSZXNvdXJjZXMRRGVtYW5kZWRSZXNvdXJjZXMBAQMDAQEBAAEAAQcDAylTeXN0ZW0uQ29sbGVjdGlvbnMuTGlzdERpY3Rpb25hcnlJbnRlcm5hbBBTeXN0ZW0uRXhjZXB0aW9uCAgCMlN5c3RlbS5TZWN1cml0eS5QZXJtaXNzaW9ucy5Ib3N0UHJvdGVjdGlvblJlc291cmNlMlN5c3RlbS5TZWN1cml0eS5QZXJtaXNzaW9ucy5Ib3N0UHJvdGVjdGlvblJlc291cmNlBgIAAAAnU3lzdGVtLlNlY3VyaXR5Lkhvc3RQcm90ZWN0aW9uRXhjZXB0aW9uBgMAAAAHbWVzc2FnZQkEAAAACQUAAAAGBgAAABlodHRwOi8vbXNkbi5taWNyb3NvZnQuY29tBgcAAAAUU3RhY2tUcmFjZSBzdHJpbmcuLi4GCAAAABtSZW1vdGUgU3RhY2tUcmFjZSBzdHJpbmcuLi4AAAAACugDAAAGCQAAABdFeGNlcHRpb25fQ2xhc3NfU2FtcGxlcwoE9v///zJTeXN0ZW0uU2VjdXJpdHkuUGVybWlzc2lvbnMuSG9zdFByb3RlY3Rpb25SZXNvdXJjZQEAAAAHdmFsdWVfXwAIAAAAAAH1////9v///wAAAAAEBAAAAClTeXN0ZW0uQ29sbGVjdGlvbnMuTGlzdERpY3Rpb25hcnlJbnRlcm5hbAMAAAAEaGVhZAd2ZXJzaW9uBWNvdW50AwAAOFN5c3RlbS5Db2xsZWN0aW9ucy5MaXN0RGljdGlvbmFyeUludGVybmFsK0RpY3Rpb25hcnlOb2RlCAgJDAAAAAIAAAACAAAABAUAAAAQU3lzdGVtLkV4Y2VwdGlvbgwAAAAJQ2xhc3NOYW1lB01lc3NhZ2UERGF0YQ5Jbm5lckV4Y2VwdGlvbgdIZWxwVVJMEFN0YWNrVHJhY2VTdHJpbmcWUmVtb3RlU3RhY2tUcmFjZVN0cmluZxBSZW1vdGVTdGFja0luZGV4D0V4Y2VwdGlvbk1ldGhvZAdIUmVzdWx0BlNvdXJjZQ1XYXRzb25CdWNrZXRzAQEDAwEBAQABAAEHKVN5c3RlbS5Db2xsZWN0aW9ucy5MaXN0RGljdGlvbmFyeUludGVybmFsEFN5c3RlbS5FeGNlcHRpb24ICAIGDQAAABBTeXN0ZW0uRXhjZXB0aW9uCQMAAAAJDwAAAAkQAAAACQYAAAAJBwAAAAkIAAAAAAAAAAroAwAACQkAAAAKBAwAAAA4U3lzdGVtLkNvbGxlY3Rpb25zLkxpc3REaWN0aW9uYXJ5SW50ZXJuYWwrRGljdGlvbmFyeU5vZGUDAAAAA2tleQV2YWx1ZQRuZXh0AgIDOFN5c3RlbS5Db2xsZWN0aW9ucy5MaXN0RGljdGlvbmFyeUludGVybmFsK0RpY3Rpb25hcnlOb2RlBhUAAAAGc2VjcmV0CAEBCRYAAAABDwAAAAQAAAAJFwAAAAIAAAACAAAAARAAAAAFAAAACQ0AAAAGGQAAABdJbm5lciBleGNlcHRpb24gbWVzc2FnZQoKCgoKAAAAAAoAFROACgoBFgAAAAwAAAAICAEAAAAGGgAAAANvbmUKARcAAAAMAAAACRUAAAAIAQEJHAAAAAEcAAAADAAAAAgIAQAAAAkaAAAACgs=", TargetFrameworkMoniker.netcoreapp20), new TypeSerializableValue("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", TargetFrameworkMoniker.netfx461) } };
 
             var hostProtectionException2 = new HostProtectionException("message", Security.Permissions.HostProtectionResource.All, Security.Permissions.HostProtectionResource.SharedState);
             yield return new object[] { PopulateException(hostProtectionException2, false), new TypeSerializableValue[] { new TypeSerializableValue("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", TargetFrameworkMoniker.netcoreapp20), new TypeSerializableValue("AAEAAAD/////AQAAAAAAAAAEAQAAACdTeXN0ZW0uU2VjdXJpdHkuSG9zdFByb3RlY3Rpb25FeGNlcHRpb24OAAAACUNsYXNzTmFtZQdNZXNzYWdlBERhdGEOSW5uZXJFeGNlcHRpb24HSGVscFVSTBBTdGFja1RyYWNlU3RyaW5nFlJlbW90ZVN0YWNrVHJhY2VTdHJpbmcQUmVtb3RlU3RhY2tJbmRleA9FeGNlcHRpb25NZXRob2QHSFJlc3VsdAZTb3VyY2UNV2F0c29uQnVja2V0cxJQcm90ZWN0ZWRSZXNvdXJjZXMRRGVtYW5kZWRSZXNvdXJjZXMBAQMDAQEBAAEAAQcDAylTeXN0ZW0uQ29sbGVjdGlvbnMuTGlzdERpY3Rpb25hcnlJbnRlcm5hbBBTeXN0ZW0uRXhjZXB0aW9uCAgCMlN5c3RlbS5TZWN1cml0eS5QZXJtaXNzaW9ucy5Ib3N0UHJvdGVjdGlvblJlc291cmNlMlN5c3RlbS5TZWN1cml0eS5QZXJtaXNzaW9ucy5Ib3N0UHJvdGVjdGlvblJlc291cmNlBgIAAAAnU3lzdGVtLlNlY3VyaXR5Lkhvc3RQcm90ZWN0aW9uRXhjZXB0aW9uBgMAAAAHbWVzc2FnZQkEAAAACgYFAAAAGWh0dHA6Ly9tc2RuLm1pY3Jvc29mdC5jb20GBgAAABRTdGFja1RyYWNlIHN0cmluZy4uLgYHAAAAG1JlbW90ZSBTdGFja1RyYWNlIHN0cmluZy4uLgAAAAAKQBYTgAYIAAAAF0V4Y2VwdGlvbl9DbGFzc19TYW1wbGVzCgT3////MlN5c3RlbS5TZWN1cml0eS5QZXJtaXNzaW9ucy5Ib3N0UHJvdGVjdGlvblJlc291cmNlAQAAAAd2YWx1ZV9fAAj/AQAAAfb////3////AgAAAAQEAAAAKVN5c3RlbS5Db2xsZWN0aW9ucy5MaXN0RGljdGlvbmFyeUludGVybmFsAwAAAARoZWFkB3ZlcnNpb24FY291bnQDAAA4U3lzdGVtLkNvbGxlY3Rpb25zLkxpc3REaWN0aW9uYXJ5SW50ZXJuYWwrRGljdGlvbmFyeU5vZGUICAkLAAAAAgAAAAIAAAAECwAAADhTeXN0ZW0uQ29sbGVjdGlvbnMuTGlzdERpY3Rpb25hcnlJbnRlcm5hbCtEaWN0aW9uYXJ5Tm9kZQMAAAADa2V5BXZhbHVlBG5leHQCAgM4U3lzdGVtLkNvbGxlY3Rpb25zLkxpc3REaWN0aW9uYXJ5SW50ZXJuYWwrRGljdGlvbmFyeU5vZGUGDAAAAAZzZWNyZXQIAQEJDQAAAAENAAAACwAAAAgIAQAAAAYOAAAAA29uZQoL", TargetFrameworkMoniker.netfx461) } };
+#pragma warning restore SYSLIB0003 // Obsolete: CAS
 
             var httpListenerException = new HttpListenerException(404, "not found");
             yield return new object[] { PopulateException(httpListenerException), new TypeSerializableValue[] { new TypeSerializableValue("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", TargetFrameworkMoniker.netcoreapp20), new TypeSerializableValue("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", TargetFrameworkMoniker.netfx461) } };
diff --git a/src/libraries/System.Runtime/ref/System.Runtime.cs b/src/libraries/System.Runtime/ref/System.Runtime.cs
index b5fb7114e9b16..447e65bd66d79 100644
--- a/src/libraries/System.Runtime/ref/System.Runtime.cs
+++ b/src/libraries/System.Runtime/ref/System.Runtime.cs
@@ -124,6 +124,7 @@ internal AppDomain() { }
         public static long MonitoringSurvivedProcessMemorySize { get { throw null; } }
         public long MonitoringTotalAllocatedMemorySize { get { throw null; } }
         public System.TimeSpan MonitoringTotalProcessorTime { get { throw null; } }
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public System.Security.PermissionSet PermissionSet { get { throw null; } }
         public string? RelativeSearchPath { get { throw null; } }
         public System.AppDomainSetup SetupInformation { get { throw null; } }
@@ -2629,7 +2630,9 @@ public LoaderOptimizationAttribute(System.LoaderOptimization value) { }
     public abstract partial class MarshalByRefObject
     {
         protected MarshalByRefObject() { }
+        [System.ObsoleteAttribute("This Remoting API is not supported and throws PlatformNotSupportedException.", DiagnosticId = "SYSLIB0010", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public object GetLifetimeService() { throw null; }
+        [System.ObsoleteAttribute("This Remoting API is not supported and throws PlatformNotSupportedException.", DiagnosticId = "SYSLIB0010", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public virtual object InitializeLifetimeService() { throw null; }
         protected System.MarshalByRefObject MemberwiseClone(bool cloneIdentity) { throw null; }
     }
@@ -7563,6 +7566,7 @@ protected Assembly() { }
         public virtual string EscapedCodeBase { get { throw null; } }
         public virtual System.Collections.Generic.IEnumerable<System.Type> ExportedTypes { [System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute("Types might be removed")] get { throw null; } }
         public virtual string? FullName { get { throw null; } }
+        [System.ObsoleteAttribute("The Global Assembly Cache is not supported.", DiagnosticId = "SYSLIB0005", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public virtual bool GlobalAssemblyCache { get { throw null; } }
         public virtual long HostContext { get { throw null; } }
         public virtual string ImageRuntimeVersion { get { throw null; } }
@@ -9364,6 +9368,7 @@ public static partial class RuntimeHelpers
         public static System.IntPtr AllocateTypeAssociatedMemory(System.Type type, int size) { throw null; }
         public static void EnsureSufficientExecutionStack() { }
         public static new bool Equals(object? o1, object? o2) { throw null; }
+        [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void ExecuteCodeWithGuaranteedCleanup(System.Runtime.CompilerServices.RuntimeHelpers.TryCode code, System.Runtime.CompilerServices.RuntimeHelpers.CleanupCode backoutCode, object? userData) { }
         public static int GetHashCode(object? o) { throw null; }
         [return: System.Diagnostics.CodeAnalysis.NotNullIfNotNullAttribute("obj")]
@@ -9372,12 +9377,16 @@ public static void ExecuteCodeWithGuaranteedCleanup(System.Runtime.CompilerServi
         public static object GetUninitializedObject([System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicConstructors | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicConstructors)] System.Type type) { throw null; }
         public static void InitializeArray(System.Array array, System.RuntimeFieldHandle fldHandle) { }
         public static bool IsReferenceOrContainsReferences<T>() { throw null; }
+        [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void PrepareConstrainedRegions() { }
+        [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void PrepareConstrainedRegionsNoOP() { }
+        [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void PrepareContractedDelegate(System.Delegate d) { }
         public static void PrepareDelegate(System.Delegate d) { }
         public static void PrepareMethod(System.RuntimeMethodHandle method) { }
         public static void PrepareMethod(System.RuntimeMethodHandle method, System.RuntimeTypeHandle[]? instantiation) { }
+        [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void ProbeForSufficientStack() { }
         public static void RunClassConstructor(System.RuntimeTypeHandle type) { }
         public static void RunModuleConstructor(System.ModuleHandle module) { }
@@ -9510,12 +9519,14 @@ public void UnsafeOnCompleted(System.Action continuation) { }
 }
 namespace System.Runtime.ConstrainedExecution
 {
+    [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public enum Cer
     {
         None = 0,
         MayFail = 1,
         Success = 2,
     }
+    [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public enum Consistency
     {
         MayCorruptProcess = 0,
@@ -9528,11 +9539,13 @@ public abstract partial class CriticalFinalizerObject
         protected CriticalFinalizerObject() { }
         ~CriticalFinalizerObject() { }
     }
+    [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Constructor | System.AttributeTargets.Method, Inherited=false)]
     public sealed partial class PrePrepareMethodAttribute : System.Attribute
     {
         public PrePrepareMethodAttribute() { }
     }
+    [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Interface | System.AttributeTargets.Method | System.AttributeTargets.Struct, Inherited=false)]
     public sealed partial class ReliabilityContractAttribute : System.Attribute
     {
@@ -10000,6 +10013,7 @@ public sealed partial class AllowPartiallyTrustedCallersAttribute : System.Attri
         public AllowPartiallyTrustedCallersAttribute() { }
         public System.Security.PartialTrustVisibilityLevel PartialTrustVisibilityLevel { get { throw null; } set { } }
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public partial interface IPermission : System.Security.ISecurityEncodable
     {
         System.Security.IPermission Copy();
@@ -10013,6 +10027,7 @@ public partial interface ISecurityEncodable
         void FromXml(System.Security.SecurityElement e);
         System.Security.SecurityElement? ToXml();
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public partial interface IStackWalk
     {
         void Assert();
@@ -10025,6 +10040,7 @@ public enum PartialTrustVisibilityLevel
         VisibleToAllHosts = 0,
         NotVisibleByDefault = 1,
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public partial class PermissionSet : System.Collections.ICollection, System.Collections.IEnumerable, System.Runtime.Serialization.IDeserializationCallback, System.Security.ISecurityEncodable, System.Security.IStackWalk
     {
         public PermissionSet(System.Security.Permissions.PermissionState state) { }
@@ -10185,32 +10201,32 @@ public CryptographicException(string format, string? insert) { }
 }
 namespace System.Security.Permissions
 {
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public abstract partial class CodeAccessSecurityAttribute : System.Security.Permissions.SecurityAttribute
     {
         protected CodeAccessSecurityAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public enum PermissionState
     {
         None = 0,
         Unrestricted = 1,
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public enum SecurityAction
     {
         Demand = 2,
         Assert = 3,
-        [System.ObsoleteAttribute("Deny is obsolete and will be removed in a future release of the .NET Framework. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         Deny = 4,
         PermitOnly = 5,
         LinkDemand = 6,
         InheritanceDemand = 7,
-        [System.ObsoleteAttribute("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestMinimum = 8,
-        [System.ObsoleteAttribute("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestOptional = 9,
-        [System.ObsoleteAttribute("Assembly level declarative security is obsolete and is no longer enforced by the CLR by default. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         RequestRefuse = 10,
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public abstract partial class SecurityAttribute : System.Attribute
     {
@@ -10219,6 +10235,7 @@ protected SecurityAttribute(System.Security.Permissions.SecurityAction action) {
         public bool Unrestricted { get { throw null; } set { } }
         public abstract System.Security.IPermission? CreatePermission();
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class SecurityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -10240,6 +10257,7 @@ public SecurityPermissionAttribute(System.Security.Permissions.SecurityAction ac
         public bool UnmanagedCode { get { throw null; } set { } }
         public override System.Security.IPermission? CreatePermission() { throw null; }
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.FlagsAttribute]
     public enum SecurityPermissionFlag
     {
@@ -10482,7 +10500,7 @@ protected Encoding(int codePage, System.Text.EncoderFallback? encoderFallback, S
         public virtual System.ReadOnlySpan<byte> Preamble { get { throw null; } }
         public static System.Text.Encoding Unicode { get { throw null; } }
         public static System.Text.Encoding UTF32 { get { throw null; } }
-        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "MSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "SYSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Text.Encoding UTF7 { get { throw null; } }
         public static System.Text.Encoding UTF8 { get { throw null; } }
         public virtual string WebName { get { throw null; } }
diff --git a/src/libraries/System.Runtime/tests/System/Runtime/ConstrainedExecution/PrePrepareMethodAttributeTests.cs b/src/libraries/System.Runtime/tests/System/Runtime/ConstrainedExecution/PrePrepareMethodAttributeTests.cs
index a48ef5552a5ed..6fc54b9247ed3 100644
--- a/src/libraries/System.Runtime/tests/System/Runtime/ConstrainedExecution/PrePrepareMethodAttributeTests.cs
+++ b/src/libraries/System.Runtime/tests/System/Runtime/ConstrainedExecution/PrePrepareMethodAttributeTests.cs
@@ -6,6 +6,7 @@
 
 namespace System.Runtime.ConstrainedExecution.Tests
 {
+#pragma warning disable SYSLIB0004 // Obsolete: CER
     public class PrePrepareMethodAttributeTests
     {
         public sealed class ConstrainedType
@@ -34,4 +35,5 @@ public void SettableOnConstructors()
                 typeof(ConstrainedType).GetConstructors()[0].GetCustomAttribute<PrePrepareMethodAttribute>());
         }
     }
+#pragma warning restore SYSLIB0004 // Obsolete: CER
 }
diff --git a/src/libraries/System.Runtime/tests/System/Text/EncodingTests.cs b/src/libraries/System.Runtime/tests/System/Text/EncodingTests.cs
index 167861387b5ba..28be1b4f7d01c 100644
--- a/src/libraries/System.Runtime/tests/System/Text/EncodingTests.cs
+++ b/src/libraries/System.Runtime/tests/System/Text/EncodingTests.cs
@@ -10,9 +10,9 @@ namespace System.Text.Tests
 {
     public class EncodingTests
     {
-#pragma warning disable MSLIB0001 // UTF7Encoding is obsolete
+#pragma warning disable SYSLIB0001 // UTF7Encoding is obsolete
         private static UTF7Encoding _utf7Encoding = new UTF7Encoding();
-#pragma warning restore MSLIB0001
+#pragma warning restore SYSLIB0001
 
         public static IEnumerable<object[]> DisallowedEncodings()
         {
diff --git a/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs b/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
index 2fb1c06526b64..355c6c239b931 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/ref/System.Security.Cryptography.Primitives.cs
@@ -16,6 +16,7 @@ protected AsymmetricAlgorithm() { }
         public virtual System.Security.Cryptography.KeySizes[] LegalKeySizes { get { throw null; } }
         public virtual string? SignatureAlgorithm { get { throw null; } }
         public void Clear() { }
+        [System.ObsoleteAttribute("The default implementation of this cryptography algorithm is not supported", DiagnosticId = "SYSLIB0007", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Security.Cryptography.AsymmetricAlgorithm Create() { throw null; }
         public static System.Security.Cryptography.AsymmetricAlgorithm? Create(string algName) { throw null; }
         public void Dispose() { }
@@ -112,6 +113,7 @@ public void Clear() { }
         public byte[] ComputeHash(byte[] buffer, int offset, int count) { throw null; }
         public byte[] ComputeHash(System.IO.Stream inputStream) { throw null; }
         public System.Threading.Tasks.Task<byte[]> ComputeHashAsync(System.IO.Stream inputStream, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        [System.ObsoleteAttribute("The default implementation of this cryptography algorithm is not supported", DiagnosticId = "SYSLIB0007", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Security.Cryptography.HashAlgorithm Create() { throw null; }
         public static System.Security.Cryptography.HashAlgorithm? Create(string hashName) { throw null; }
         public void Dispose() { }
@@ -151,6 +153,7 @@ protected HMAC() { }
         protected int BlockSizeValue { get { throw null; } set { } }
         public string HashName { get { throw null; } set { } }
         public override byte[] Key { get { throw null; } set { } }
+        [System.ObsoleteAttribute("The default implementation of this cryptography algorithm is not supported", DiagnosticId = "SYSLIB0007", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static new System.Security.Cryptography.HMAC Create() { throw null; }
         public static new System.Security.Cryptography.HMAC? Create(string algorithmName) { throw null; }
         protected override void Dispose(bool disposing) { }
@@ -174,6 +177,7 @@ public abstract partial class KeyedHashAlgorithm : System.Security.Cryptography.
         protected byte[] KeyValue;
         protected KeyedHashAlgorithm() { }
         public virtual byte[] Key { get { throw null; } set { } }
+        [System.ObsoleteAttribute("The default implementation of this cryptography algorithm is not supported", DiagnosticId = "SYSLIB0007", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static new System.Security.Cryptography.KeyedHashAlgorithm Create() { throw null; }
         public static new System.Security.Cryptography.KeyedHashAlgorithm? Create(string algName) { throw null; }
         protected override void Dispose(bool disposing) { }
@@ -230,6 +234,7 @@ protected SymmetricAlgorithm() { }
         public virtual System.Security.Cryptography.CipherMode Mode { get { throw null; } set { } }
         public virtual System.Security.Cryptography.PaddingMode Padding { get { throw null; } set { } }
         public void Clear() { }
+        [System.ObsoleteAttribute("The default implementation of this cryptography algorithm is not supported", DiagnosticId = "SYSLIB0007", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static System.Security.Cryptography.SymmetricAlgorithm Create() { throw null; }
         public static System.Security.Cryptography.SymmetricAlgorithm? Create(string algName) { throw null; }
         public virtual System.Security.Cryptography.ICryptoTransform CreateDecryptor() { throw null; }
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj b/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
index 6a479c3c92988..1d98480074523 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System.Security.Cryptography.Primitives.csproj
@@ -27,6 +27,8 @@
     <Compile Include="System\Security\Cryptography\PbeEncryptionAlgorithm.cs" />
     <Compile Include="System\Security\Cryptography\PbeParameters.cs" />
     <Compile Include="System\Security\Cryptography\SymmetricAlgorithm.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs"
+             Link="Common\System\Obsoletions.cs" />
     <Compile Include="$(CommonPath)System\Threading\Tasks\ForceAsyncAwaiter.cs"
              Link="Common\System\Threading\Tasks\ForceAsyncAwaiter.cs" />
     <Compile Include="$(CommonPath)Internal\Cryptography\Helpers.cs"
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/AsymmetricAlgorithm.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/AsymmetricAlgorithm.cs
index 2e2c15961427a..c42ecd4eac0a2 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/AsymmetricAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/AsymmetricAlgorithm.cs
@@ -13,6 +13,7 @@ public abstract class AsymmetricAlgorithm : IDisposable
 
         protected AsymmetricAlgorithm() { }
 
+        [Obsolete(Obsoletions.DefaultCryptoAlgorithmsMessage, DiagnosticId = Obsoletions.DefaultCryptoAlgorithmsDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static AsymmetricAlgorithm Create() =>
             throw new PlatformNotSupportedException(SR.Cryptography_DefaultAlgorithm_NotSupported);
 
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HMAC.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HMAC.cs
index 646f48670b19c..4268cd99a4424 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HMAC.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HMAC.cs
@@ -16,6 +16,7 @@ protected int BlockSizeValue
 
         protected HMAC() { }
 
+        [Obsolete(Obsoletions.DefaultCryptoAlgorithmsMessage, DiagnosticId = Obsoletions.DefaultCryptoAlgorithmsDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static new HMAC Create() =>
             throw new PlatformNotSupportedException(SR.Cryptography_DefaultAlgorithm_NotSupported);
 
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HashAlgorithm.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HashAlgorithm.cs
index e953c84751b5f..31d64ebd0157f 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HashAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/HashAlgorithm.cs
@@ -17,6 +17,7 @@ public abstract class HashAlgorithm : IDisposable, ICryptoTransform
 
         protected HashAlgorithm() { }
 
+        [Obsolete(Obsoletions.DefaultCryptoAlgorithmsMessage, DiagnosticId = Obsoletions.DefaultCryptoAlgorithmsDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static HashAlgorithm Create() =>
             CryptoConfigForwarder.CreateDefaultHashAlgorithm();
 
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/KeyedHashAlgorithm.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/KeyedHashAlgorithm.cs
index 9237f482b267a..2088346bbe074 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/KeyedHashAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/KeyedHashAlgorithm.cs
@@ -9,6 +9,7 @@ public abstract class KeyedHashAlgorithm : HashAlgorithm
     {
         protected KeyedHashAlgorithm() { }
 
+        [Obsolete(Obsoletions.DefaultCryptoAlgorithmsMessage, DiagnosticId = Obsoletions.DefaultCryptoAlgorithmsDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static new KeyedHashAlgorithm Create() =>
             throw new PlatformNotSupportedException(SR.Cryptography_DefaultAlgorithm_NotSupported);
 
diff --git a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/SymmetricAlgorithm.cs b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/SymmetricAlgorithm.cs
index 1e0247c724d87..8e16664690e1c 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/SymmetricAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/src/System/Security/Cryptography/SymmetricAlgorithm.cs
@@ -15,6 +15,7 @@ protected SymmetricAlgorithm()
             PaddingValue = PaddingMode.PKCS7;
         }
 
+        [Obsolete(Obsoletions.DefaultCryptoAlgorithmsMessage, DiagnosticId = Obsoletions.DefaultCryptoAlgorithmsDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public static SymmetricAlgorithm Create() =>
             throw new PlatformNotSupportedException(SR.Cryptography_DefaultAlgorithm_NotSupported);
 
diff --git a/src/libraries/System.Security.Cryptography.Primitives/tests/CryptoConfigTests.cs b/src/libraries/System.Security.Cryptography.Primitives/tests/CryptoConfigTests.cs
index 3184a8d247af3..7dcdd650ea27f 100644
--- a/src/libraries/System.Security.Cryptography.Primitives/tests/CryptoConfigTests.cs
+++ b/src/libraries/System.Security.Cryptography.Primitives/tests/CryptoConfigTests.cs
@@ -10,12 +10,14 @@ public static class CryptoConfigTests
         [Fact]
         public static void DefaultStaticCreateMethods()
         {
+#pragma warning disable SYSLIB0007 // These methods are marked as Obsolete
             // .NET Core does not allow the base classes to pick an algorithm.
             Assert.Throws<PlatformNotSupportedException>(() => AsymmetricAlgorithm.Create());
             Assert.Throws<PlatformNotSupportedException>(() => HashAlgorithm.Create());
             Assert.Throws<PlatformNotSupportedException>(() => KeyedHashAlgorithm.Create());
             Assert.Throws<PlatformNotSupportedException>(() => HMAC.Create());
             Assert.Throws<PlatformNotSupportedException>(() => SymmetricAlgorithm.Create());
+#pragma warning restore SYSLIB0007
         }
 
         [Fact]
diff --git a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.Forwards.cs b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.Forwards.cs
index 6346b1c040307..6e691f997d500 100644
--- a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.Forwards.cs
+++ b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.Forwards.cs
@@ -3,6 +3,7 @@
 // ------------------------------------------------------------------------------
 // Changes to this file must follow the https://aka.ms/api-review process.
 // ------------------------------------------------------------------------------
+#pragma warning disable SYSLIB0003 // CAS Obsoletions
 
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Security.IPermission))]
 [assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Security.ISecurityEncodable))]
diff --git a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.cs b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.cs
index 1af660f5a3736..81c59db3baa11 100644
--- a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.cs
+++ b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.cs
@@ -17,6 +17,9 @@ void System.Runtime.Serialization.ISerializable.GetObjectData(System.Runtime.Ser
 }
 namespace System.Configuration
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class ConfigurationPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public ConfigurationPermission(System.Security.Permissions.PermissionState state) { }
@@ -29,6 +32,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.All, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class ConfigurationPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public ConfigurationPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -37,6 +43,9 @@ public ConfigurationPermissionAttribute(System.Security.Permissions.SecurityActi
 }
 namespace System.Data.Common
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public abstract partial class DBDataPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         protected DBDataPermission() { }
@@ -56,6 +65,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public abstract partial class DBDataPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -72,6 +84,9 @@ protected DBDataPermissionAttribute(System.Security.Permissions.SecurityAction a
 }
 namespace System.Data.Odbc
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class OdbcPermission : System.Data.Common.DBDataPermission
     {
         public OdbcPermission() { }
@@ -80,6 +95,9 @@ public OdbcPermission(System.Security.Permissions.PermissionState state, bool al
         public override void Add(string connectionString, string restrictions, System.Data.KeyRestrictionBehavior behavior) { }
         public override System.Security.IPermission Copy() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class OdbcPermissionAttribute : System.Data.Common.DBDataPermissionAttribute
     {
@@ -89,6 +107,9 @@ public OdbcPermissionAttribute(System.Security.Permissions.SecurityAction action
 }
 namespace System.Data.OleDb
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class OleDbPermission : System.Data.Common.DBDataPermission
     {
         public OleDbPermission() { }
@@ -99,6 +120,9 @@ public OleDbPermission(System.Security.Permissions.PermissionState state, bool a
         public string Provider { get { throw null; } set { } }
         public override System.Security.IPermission Copy() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class OleDbPermissionAttribute : System.Data.Common.DBDataPermissionAttribute
     {
@@ -111,6 +135,9 @@ public OleDbPermissionAttribute(System.Security.Permissions.SecurityAction actio
 }
 namespace System.Data.OracleClient
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class OraclePermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public OraclePermission(System.Security.Permissions.PermissionState state) { }
@@ -124,6 +151,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class OraclePermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -141,6 +171,9 @@ public OraclePermissionAttribute(System.Security.Permissions.SecurityAction acti
 }
 namespace System.Data.SqlClient
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SqlClientPermission : System.Data.Common.DBDataPermission
     {
         public SqlClientPermission() { }
@@ -149,6 +182,9 @@ public SqlClientPermission(System.Security.Permissions.PermissionState state, bo
         public override void Add(string connectionString, string restrictions, System.Data.KeyRestrictionBehavior behavior) { }
         public override System.Security.IPermission Copy() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class SqlClientPermissionAttribute : System.Data.Common.DBDataPermissionAttribute
     {
@@ -158,6 +194,9 @@ public SqlClientPermissionAttribute(System.Security.Permissions.SecurityAction a
 }
 namespace System.Diagnostics
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class EventLogPermission : System.Security.Permissions.ResourcePermissionBase
     {
         public EventLogPermission() { }
@@ -176,6 +215,9 @@ public enum EventLogPermissionAccess
         Write = 16,
         Administer = 48,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Event | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public partial class EventLogPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -207,6 +249,9 @@ protected override void OnRemove(int index, object value) { }
         protected override void OnSet(int index, object oldValue, object newValue) { }
         public void Remove(System.Diagnostics.EventLogPermissionEntry value) { }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PerformanceCounterPermission : System.Security.Permissions.ResourcePermissionBase
     {
         public PerformanceCounterPermission() { }
@@ -225,6 +270,9 @@ public enum PerformanceCounterPermissionAccess
         Instrument = 3,
         Administer = 7,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Event | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public partial class PerformanceCounterPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -261,6 +309,9 @@ public void Remove(System.Diagnostics.PerformanceCounterPermissionEntry value) {
 }
 namespace System.Drawing.Printing
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PrintingPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public PrintingPermission(System.Drawing.Printing.PrintingPermissionLevel printingLevel) { }
@@ -274,6 +325,9 @@ public override void FromXml(System.Security.SecurityElement element) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.All, AllowMultiple=true)]
     public sealed partial class PrintingPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -291,6 +345,9 @@ public enum PrintingPermissionLevel
 }
 namespace System.Net
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class DnsPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public DnsPermission(System.Security.Permissions.PermissionState state) { }
@@ -302,6 +359,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class DnsPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -323,6 +383,9 @@ public enum NetworkAccess
         Connect = 64,
         Accept = 128,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SocketPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public const int AllPorts = -1;
@@ -340,6 +403,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SocketPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public SocketPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -357,6 +423,9 @@ public enum TransportType
         Tcp = 2,
         All = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class WebPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public WebPermission() { }
@@ -376,6 +445,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class WebPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public WebPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -394,6 +466,9 @@ public enum SmtpAccess
         Connect = 1,
         ConnectToUnrestrictedPort = 2,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SmtpPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public SmtpPermission(bool unrestricted) { }
@@ -409,6 +484,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class SmtpPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -426,6 +504,9 @@ public enum NetworkInformationAccess
         Read = 1,
         Ping = 4,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class NetworkInformationPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public NetworkInformationPermission(System.Net.NetworkInformation.NetworkInformationAccess access) { }
@@ -440,6 +521,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class NetworkInformationPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -450,6 +534,9 @@ public NetworkInformationPermissionAttribute(System.Security.Permissions.Securit
 }
 namespace System.Net.PeerToPeer
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PnrpPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public PnrpPermission(System.Security.Permissions.PermissionState state) { }
@@ -461,6 +548,9 @@ public override void FromXml(System.Security.SecurityElement e) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class PnrpPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -477,6 +567,9 @@ public enum PnrpScope
 }
 namespace System.Net.PeerToPeer.Collaboration
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PeerCollaborationPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public PeerCollaborationPermission(System.Security.Permissions.PermissionState state) { }
@@ -488,6 +581,9 @@ public override void FromXml(System.Security.SecurityElement e) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class PeerCollaborationPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -497,6 +593,9 @@ public PeerCollaborationPermissionAttribute(System.Security.Permissions.Security
 }
 namespace System.Security
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public abstract partial class CodeAccessPermission : System.Security.IPermission, System.Security.ISecurityEncodable, System.Security.IStackWalk
     {
         protected CodeAccessPermission() { }
@@ -520,6 +619,9 @@ public static void RevertPermitOnly() { }
         public abstract System.Security.SecurityElement ToXml();
         public virtual System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public partial class HostProtectionException : System.SystemException
     {
         public HostProtectionException() { }
@@ -574,6 +676,9 @@ public partial interface IStackWalk
         void Deny();
         void PermitOnly();
     }
+#endif
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
 #endif
     public sealed partial class NamedPermissionSet : System.Security.PermissionSet
     {
@@ -658,6 +763,9 @@ public enum SecurityContextSource
         CurrentAppDomain = 0,
         CurrentAssembly = 1,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public static partial class SecurityManager
     {
         [System.ObsoleteAttribute]
@@ -716,6 +824,9 @@ public XmlSyntaxException(string message, System.Exception inner) { }
 }
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class DataProtectionPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public DataProtectionPermission(System.Security.Permissions.DataProtectionPermissionFlags flag) { }
@@ -729,6 +840,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class DataProtectionPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -740,6 +854,9 @@ public DataProtectionPermissionAttribute(System.Security.Permissions.SecurityAct
         public bool UnprotectMemory { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum DataProtectionPermissionFlags
     {
@@ -750,6 +867,9 @@ public enum DataProtectionPermissionFlags
         UnprotectMemory = 8,
         AllFlags = 15,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class EnvironmentPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public EnvironmentPermission(System.Security.Permissions.EnvironmentPermissionAccess flag, string pathList) { }
@@ -766,6 +886,9 @@ public void SetPathList(System.Security.Permissions.EnvironmentPermissionAccess
         public override System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
     [System.FlagsAttribute]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum EnvironmentPermissionAccess
     {
         NoAccess = 0,
@@ -774,6 +897,9 @@ public enum EnvironmentPermissionAccess
         AllAccess = 3,
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class EnvironmentPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public EnvironmentPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -782,6 +908,9 @@ public EnvironmentPermissionAttribute(System.Security.Permissions.SecurityAction
         public string Write { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class FileDialogPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public FileDialogPermission(System.Security.Permissions.FileDialogPermissionAccess access) { }
@@ -795,6 +924,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum FileDialogPermissionAccess
     {
@@ -803,6 +935,9 @@ public enum FileDialogPermissionAccess
         Save = 2,
         OpenSave = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class FileDialogPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -811,6 +946,9 @@ public FileDialogPermissionAttribute(System.Security.Permissions.SecurityAction
         public bool Save { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class FileIOPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public FileIOPermission(System.Security.Permissions.FileIOPermissionAccess access, System.Security.AccessControl.AccessControlActions actions, string path) { }
@@ -835,6 +973,9 @@ public void SetPathList(System.Security.Permissions.FileIOPermissionAccess acces
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum FileIOPermissionAccess
     {
@@ -845,6 +986,9 @@ public enum FileIOPermissionAccess
         PathDiscovery = 8,
         AllAccess = 15,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class FileIOPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -862,6 +1006,9 @@ public FileIOPermissionAttribute(System.Security.Permissions.SecurityAction acti
         public string Write { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class GacIdentityPermission : System.Security.CodeAccessPermission
     {
         public GacIdentityPermission() { }
@@ -873,12 +1020,18 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class GacIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public GacIdentityPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Delegate | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class HostProtectionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -896,6 +1049,9 @@ public HostProtectionAttribute(System.Security.Permissions.SecurityAction action
         public bool UI { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum HostProtectionResource
     {
@@ -911,6 +1067,9 @@ public enum HostProtectionResource
         MayLeakOnAbort = 256,
         All = 511,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum IsolatedStorageContainment
     {
         None = 0,
@@ -926,6 +1085,9 @@ public enum IsolatedStorageContainment
         AdministerIsolatedStorageByUser = 112,
         UnrestrictedIsolatedStorage = 240,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class IsolatedStorageFilePermission : System.Security.Permissions.IsolatedStoragePermission
     {
         public IsolatedStorageFilePermission(System.Security.Permissions.PermissionState state) : base (default(System.Security.Permissions.PermissionState)) { }
@@ -935,12 +1097,18 @@ public IsolatedStorageFilePermission(System.Security.Permissions.PermissionState
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class IsolatedStorageFilePermissionAttribute : System.Security.Permissions.IsolatedStoragePermissionAttribute
     {
         public IsolatedStorageFilePermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public abstract partial class IsolatedStoragePermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         protected IsolatedStoragePermission(System.Security.Permissions.PermissionState state) { }
@@ -950,16 +1118,25 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public bool IsUnrestricted() { throw null; }
         public override System.Security.SecurityElement ToXml() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public abstract partial class IsolatedStoragePermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         protected IsolatedStoragePermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
         public System.Security.Permissions.IsolatedStorageContainment UsageAllowed { get { throw null; } set { } }
         public long UserQuota { get { throw null; } set { } }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public partial interface IUnrestrictedPermission
     {
         bool IsUnrestricted();
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class KeyContainerPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public KeyContainerPermission(System.Security.Permissions.KeyContainerPermissionFlags flags) { }
@@ -975,6 +1152,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class KeyContainerPermissionAccessEntry
     {
         public KeyContainerPermissionAccessEntry(System.Security.Cryptography.CspParameters parameters, System.Security.Permissions.KeyContainerPermissionFlags flags) { }
@@ -989,6 +1169,9 @@ public KeyContainerPermissionAccessEntry(string keyStore, string providerName, i
         public override bool Equals(object o) { throw null; }
         public override int GetHashCode() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class KeyContainerPermissionAccessEntryCollection : System.Collections.ICollection, System.Collections.IEnumerable
     {
         public KeyContainerPermissionAccessEntryCollection() { }
@@ -1005,6 +1188,9 @@ public void CopyTo(System.Security.Permissions.KeyContainerPermissionAccessEntry
         public void Remove(System.Security.Permissions.KeyContainerPermissionAccessEntry accessEntry) { }
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class KeyContainerPermissionAccessEntryEnumerator : System.Collections.IEnumerator
     {
         public KeyContainerPermissionAccessEntryEnumerator() { }
@@ -1014,6 +1200,9 @@ public KeyContainerPermissionAccessEntryEnumerator() { }
         public void Reset() { }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class KeyContainerPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public KeyContainerPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -1025,6 +1214,9 @@ public KeyContainerPermissionAttribute(System.Security.Permissions.SecurityActio
         public int ProviderType { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum KeyContainerPermissionFlags
     {
         NoFlags = 0,
@@ -1039,6 +1231,9 @@ public enum KeyContainerPermissionFlags
         ChangeAcl = 8192,
         AllFlags = 13111,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class MediaPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public MediaPermission() { }
@@ -1059,6 +1254,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class MediaPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public MediaPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -1067,6 +1265,9 @@ public MediaPermissionAttribute(System.Security.Permissions.SecurityAction actio
         public System.Security.Permissions.MediaPermissionVideo Video { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum MediaPermissionAudio
     {
         NoAudio = 0,
@@ -1074,6 +1275,9 @@ public enum MediaPermissionAudio
         SafeAudio = 2,
         AllAudio = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum MediaPermissionImage
     {
         NoImage = 0,
@@ -1081,6 +1285,9 @@ public enum MediaPermissionImage
         SafeImage = 2,
         AllImage = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum MediaPermissionVideo
     {
         NoVideo = 0,
@@ -1088,6 +1295,9 @@ public enum MediaPermissionVideo
         SafeVideo = 2,
         AllVideo = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class PermissionSetAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1106,6 +1316,9 @@ public enum PermissionState
         None = 0,
         Unrestricted = 1,
     }
+#endif
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
 #endif
     public sealed partial class PrincipalPermission : System.Security.IPermission, System.Security.ISecurityEncodable, System.Security.Permissions.IUnrestrictedPermission
     {
@@ -1125,10 +1338,13 @@ public void FromXml(System.Security.SecurityElement elem) { }
         public System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
     [System.AttributeUsageAttribute(System.AttributeTargets.Class | System.AttributeTargets.Method, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PrincipalPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
-#if CAS_OBSOLETIONS
-        [System.ObsoleteAttribute("PrincipalPermissionAttribute is not honored by the runtime and must not be used.", true, DiagnosticId = "MSLIB0002", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("PrincipalPermissionAttribute is not honored by the runtime and must not be used.", true, DiagnosticId = "SYSLIB0002", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
 #endif
         public PrincipalPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
         public bool Authenticated { get { throw null; } set { } }
@@ -1136,6 +1352,9 @@ public PrincipalPermissionAttribute(System.Security.Permissions.SecurityAction a
         public string Role { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class PublisherIdentityPermission : System.Security.CodeAccessPermission
     {
         public PublisherIdentityPermission(System.Security.Cryptography.X509Certificates.X509Certificate certificate) { }
@@ -1148,6 +1367,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class PublisherIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1157,6 +1379,9 @@ public PublisherIdentityPermissionAttribute(System.Security.Permissions.Security
         public string X509Certificate { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class ReflectionPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public ReflectionPermission(System.Security.Permissions.PermissionState state) { }
@@ -1170,6 +1395,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class ReflectionPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1183,6 +1411,9 @@ public ReflectionPermissionAttribute(System.Security.Permissions.SecurityAction
         public bool TypeInformation { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum ReflectionPermissionFlag
     {
@@ -1196,6 +1427,9 @@ public enum ReflectionPermissionFlag
         AllFlags = 7,
         RestrictedMemberAccess = 8,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class RegistryPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public RegistryPermission(System.Security.Permissions.PermissionState state) { }
@@ -1213,6 +1447,9 @@ public void SetPathList(System.Security.Permissions.RegistryPermissionAccess acc
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission other) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum RegistryPermissionAccess
     {
@@ -1222,6 +1459,9 @@ public enum RegistryPermissionAccess
         Create = 4,
         AllAccess = 7,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class RegistryPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1236,6 +1476,9 @@ public RegistryPermissionAttribute(System.Security.Permissions.SecurityAction ac
         public string Write { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public abstract partial class ResourcePermissionBase : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public const string Any = "*";
@@ -1256,6 +1499,9 @@ protected void RemovePermissionAccess(System.Security.Permissions.ResourcePermis
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public partial class ResourcePermissionBaseEntry
     {
         public ResourcePermissionBaseEntry() { }
@@ -1263,6 +1509,9 @@ public ResourcePermissionBaseEntry(int permissionAccess, string[] permissionAcce
         public int PermissionAccess { get { throw null; } }
         public string[] PermissionAccessPath { get { throw null; } }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SecurityPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public SecurityPermission(System.Security.Permissions.PermissionState state) { }
@@ -1276,6 +1525,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class SiteIdentityPermission : System.Security.CodeAccessPermission
     {
         public SiteIdentityPermission(System.Security.Permissions.PermissionState state) { }
@@ -1288,6 +1540,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class SiteIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1295,6 +1550,9 @@ public SiteIdentityPermissionAttribute(System.Security.Permissions.SecurityActio
         public string Site { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class StorePermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public StorePermission(System.Security.Permissions.PermissionState state) { }
@@ -1308,6 +1566,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class StorePermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1322,6 +1583,9 @@ public StorePermissionAttribute(System.Security.Permissions.SecurityAction actio
         public bool RemoveFromStore { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum StorePermissionFlags
     {
@@ -1335,6 +1599,9 @@ public enum StorePermissionFlags
         EnumerateCertificates = 128,
         AllFlags = 247,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class StrongNameIdentityPermission : System.Security.CodeAccessPermission
     {
         public StrongNameIdentityPermission(System.Security.Permissions.PermissionState state) { }
@@ -1349,6 +1616,9 @@ public override void FromXml(System.Security.SecurityElement e) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class StrongNameIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1358,6 +1628,9 @@ public StrongNameIdentityPermissionAttribute(System.Security.Permissions.Securit
         public string Version { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class StrongNamePublicKeyBlob
     {
         public StrongNamePublicKeyBlob(byte[] publicKey) { }
@@ -1365,6 +1638,9 @@ public StrongNamePublicKeyBlob(byte[] publicKey) { }
         public override int GetHashCode() { throw null; }
         public override string ToString() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class TypeDescriptorPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public TypeDescriptorPermission(System.Security.Permissions.PermissionState state) { }
@@ -1378,6 +1654,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class TypeDescriptorPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1386,12 +1665,18 @@ public TypeDescriptorPermissionAttribute(System.Security.Permissions.SecurityAct
         public bool RestrictedRegistrationAccess { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.FlagsAttribute]
     public enum TypeDescriptorPermissionFlags
     {
         NoFlags = 0,
         RestrictedRegistrationAccess = 1,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class UIPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public UIPermission(System.Security.Permissions.PermissionState state) { }
@@ -1408,6 +1693,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class UIPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1416,12 +1704,18 @@ public UIPermissionAttribute(System.Security.Permissions.SecurityAction action)
         public System.Security.Permissions.UIPermissionWindow Window { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum UIPermissionClipboard
     {
         NoClipboard = 0,
         OwnClipboard = 1,
         AllClipboard = 2,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum UIPermissionWindow
     {
         NoWindows = 0,
@@ -1429,6 +1723,9 @@ public enum UIPermissionWindow
         SafeTopLevelWindows = 2,
         AllWindows = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class UrlIdentityPermission : System.Security.CodeAccessPermission
     {
         public UrlIdentityPermission(System.Security.Permissions.PermissionState state) { }
@@ -1441,6 +1738,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class UrlIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1448,6 +1748,9 @@ public UrlIdentityPermissionAttribute(System.Security.Permissions.SecurityAction
         public string Url { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class WebBrowserPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public WebBrowserPermission() { }
@@ -1462,6 +1765,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class WebBrowserPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1469,12 +1775,18 @@ public WebBrowserPermissionAttribute(System.Security.Permissions.SecurityAction
         public System.Security.Permissions.WebBrowserPermissionLevel Level { get { throw null; } set { } }
         public override System.Security.IPermission CreatePermission() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public enum WebBrowserPermissionLevel
     {
         None = 0,
         Safe = 1,
         Unrestricted = 2,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class ZoneIdentityPermission : System.Security.CodeAccessPermission
     {
         public ZoneIdentityPermission(System.Security.Permissions.PermissionState state) { }
@@ -1487,6 +1799,9 @@ public override void FromXml(System.Security.SecurityElement esd) { }
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public sealed partial class ZoneIdentityPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -1536,10 +1851,16 @@ public sealed partial class ApplicationTrust : System.Security.Policy.EvidenceBa
     {
         public ApplicationTrust() { }
         public ApplicationTrust(System.ApplicationIdentity identity) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public ApplicationTrust(System.Security.PermissionSet defaultGrantSet, System.Collections.Generic.IEnumerable<System.Security.Policy.StrongName> fullTrustAssemblies) { }
         public System.ApplicationIdentity ApplicationIdentity { get { throw null; } set { } }
         public System.Security.Policy.PolicyStatement DefaultGrantSet { get { throw null; } set { } }
         public object ExtraInfo { get { throw null; } set { } }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Collections.Generic.IList<System.Security.Policy.StrongName> FullTrustAssemblies { get { throw null; } }
         public bool IsApplicationTrustedToRun { get { throw null; } set { } }
         public bool Persist { get { throw null; } set { } }
@@ -1658,6 +1979,9 @@ public abstract partial class EvidenceBase
         protected EvidenceBase() { }
         public virtual System.Security.Policy.EvidenceBase Clone() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class FileCodeGroup : System.Security.Policy.CodeGroup
     {
         public FileCodeGroup(System.Security.Policy.IMembershipCondition membershipCondition, System.Security.Permissions.FileIOPermissionAccess access) : base (default(System.Security.Policy.IMembershipCondition), default(System.Security.Policy.PolicyStatement)) { }
@@ -1681,6 +2005,9 @@ public sealed partial class FirstMatchCodeGroup : System.Security.Policy.CodeGro
         public override System.Security.Policy.PolicyStatement Resolve(System.Security.Policy.Evidence evidence) { throw null; }
         public override System.Security.Policy.CodeGroup ResolveMatchingCodeGroups(System.Security.Policy.Evidence evidence) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class GacInstalled : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public GacInstalled() { }
@@ -1733,6 +2060,9 @@ void System.Runtime.Serialization.ISerializable.GetObjectData(System.Runtime.Ser
         public System.Security.SecurityElement ToXml() { throw null; }
         public System.Security.SecurityElement ToXml(System.Security.Policy.PolicyLevel level) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public partial interface IIdentityPermissionFactory
     {
         System.Security.IPermission CreateIdentityPermission(System.Security.Policy.Evidence evidence);
@@ -1794,18 +2124,33 @@ internal PolicyLevel() { }
         public void AddFullTrustAssembly(System.Security.Policy.StrongName sn) { }
         [System.ObsoleteAttribute]
         public void AddFullTrustAssembly(System.Security.Policy.StrongNameMembershipCondition snMC) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public void AddNamedPermissionSet(System.Security.NamedPermissionSet permSet) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Security.NamedPermissionSet ChangeNamedPermissionSet(string name, System.Security.PermissionSet pSet) { throw null; }
         [System.ObsoleteAttribute("AppDomain policy levels are obsolete. See https://go.microsoft.com/fwlink/?LinkID=155570 for more information.")]
         public static System.Security.Policy.PolicyLevel CreateAppDomainLevel() { throw null; }
         public void FromXml(System.Security.SecurityElement e) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Security.NamedPermissionSet GetNamedPermissionSet(string name) { throw null; }
         public void Recover() { }
         [System.ObsoleteAttribute]
         public void RemoveFullTrustAssembly(System.Security.Policy.StrongName sn) { }
         [System.ObsoleteAttribute]
         public void RemoveFullTrustAssembly(System.Security.Policy.StrongNameMembershipCondition snMC) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Security.NamedPermissionSet RemoveNamedPermissionSet(System.Security.NamedPermissionSet permSet) { throw null; }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Security.NamedPermissionSet RemoveNamedPermissionSet(string name) { throw null; }
         public void Reset() { }
         public System.Security.Policy.PolicyStatement Resolve(System.Security.Policy.Evidence evidence) { throw null; }
@@ -1814,10 +2159,19 @@ public void Reset() { }
     }
     public sealed partial class PolicyStatement : System.Security.ISecurityEncodable, System.Security.ISecurityPolicyEncodable
     {
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public PolicyStatement(System.Security.PermissionSet permSet) { }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public PolicyStatement(System.Security.PermissionSet permSet, System.Security.Policy.PolicyStatementAttribute attributes) { }
         public System.Security.Policy.PolicyStatementAttribute Attributes { get { throw null; } set { } }
         public string AttributeString { get { throw null; } }
+#if NET50_OBSOLETIONS
+        [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
         public System.Security.PermissionSet PermissionSet { get { throw null; } set { } }
         public System.Security.Policy.PolicyStatement Copy() { throw null; }
         public override bool Equals(object o) { throw null; }
@@ -1835,6 +2189,9 @@ public enum PolicyStatementAttribute
         LevelFinal = 2,
         All = 3,
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class Publisher : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public Publisher(System.Security.Cryptography.X509Certificates.X509Certificate cert) { }
@@ -1859,6 +2216,9 @@ public void FromXml(System.Security.SecurityElement e, System.Security.Policy.Po
         public System.Security.SecurityElement ToXml() { throw null; }
         public System.Security.SecurityElement ToXml(System.Security.Policy.PolicyLevel level) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class Site : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public Site(string name) { }
@@ -1884,6 +2244,9 @@ public void FromXml(System.Security.SecurityElement e, System.Security.Policy.Po
         public System.Security.SecurityElement ToXml() { throw null; }
         public System.Security.SecurityElement ToXml(System.Security.Policy.PolicyLevel level) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class StrongName : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public StrongName(System.Security.Permissions.StrongNamePublicKeyBlob blob, string name, System.Version version) { }
@@ -1896,6 +2259,9 @@ public StrongName(System.Security.Permissions.StrongNamePublicKeyBlob blob, stri
         public override int GetHashCode() { throw null; }
         public override string ToString() { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class StrongNameMembershipCondition : System.Security.ISecurityEncodable, System.Security.ISecurityPolicyEncodable, System.Security.Policy.IMembershipCondition
     {
         public StrongNameMembershipCondition(System.Security.Permissions.StrongNamePublicKeyBlob blob, string name, System.Version version) { }
@@ -1938,6 +2304,9 @@ public sealed partial class UnionCodeGroup : System.Security.Policy.CodeGroup
         public override System.Security.Policy.PolicyStatement Resolve(System.Security.Policy.Evidence evidence) { throw null; }
         public override System.Security.Policy.CodeGroup ResolveMatchingCodeGroups(System.Security.Policy.Evidence evidence) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class Url : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public Url(string name) { }
@@ -1962,6 +2331,9 @@ public void FromXml(System.Security.SecurityElement e, System.Security.Policy.Po
         public System.Security.SecurityElement ToXml() { throw null; }
         public System.Security.SecurityElement ToXml(System.Security.Policy.PolicyLevel level) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class Zone : System.Security.Policy.EvidenceBase, System.Security.Policy.IIdentityPermissionFactory
     {
         public Zone(System.Security.SecurityZone zone) { }
@@ -1990,6 +2362,9 @@ public void FromXml(System.Security.SecurityElement e, System.Security.Policy.Po
 }
 namespace System.ServiceProcess
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class ServiceControllerPermission : System.Security.Permissions.ResourcePermissionBase
     {
         public ServiceControllerPermission() { }
@@ -2005,7 +2380,10 @@ public enum ServiceControllerPermissionAccess
         Browse = 2,
         Control = 6,
     }
-    [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Event | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
+    [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Event | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple = true, Inherited = false)]
     public partial class ServiceControllerPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
         public ServiceControllerPermissionAttribute(System.Security.Permissions.SecurityAction action) : base (default(System.Security.Permissions.SecurityAction)) { }
@@ -2042,6 +2420,9 @@ public void Remove(System.ServiceProcess.ServiceControllerPermissionEntry value)
 }
 namespace System.Transactions
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class DistributedTransactionPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public DistributedTransactionPermission(System.Security.Permissions.PermissionState state) { }
@@ -2053,6 +2434,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.All, AllowMultiple=true)]
     public sealed partial class DistributedTransactionPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
@@ -2063,6 +2447,9 @@ public DistributedTransactionPermissionAttribute(System.Security.Permissions.Sec
 }
 namespace System.Web
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class AspNetHostingPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public AspNetHostingPermission(System.Security.Permissions.PermissionState state) { }
@@ -2076,6 +2463,9 @@ public override void FromXml(System.Security.SecurityElement securityElement) {
         public override System.Security.SecurityElement ToXml() { throw null; }
         public override System.Security.IPermission Union(System.Security.IPermission target) { throw null; }
     }
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     [System.AttributeUsageAttribute(System.AttributeTargets.All, AllowMultiple=true, Inherited=false)]
     public sealed partial class AspNetHostingPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.csproj b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.csproj
index ec7d4c444af70..9905b3157eef5 100644
--- a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.csproj
+++ b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.csproj
@@ -7,8 +7,9 @@
   <PropertyGroup>
     <IsPartialFacadeAssembly Condition="$(TargetFramework.StartsWith('net4'))">true</IsPartialFacadeAssembly>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
-    <DefineConstants>$(DefineConstants);CAS_OBSOLETIONS</DefineConstants>
+  <!-- We conditionally apply net5.0+ obsoletions -->
+  <PropertyGroup Condition="!($(TargetFramework.StartsWith('netcoreapp')) or $(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net4')))">
+    <DefineConstants>$(DefineConstants);NET50_OBSOLETIONS</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.Security.Permissions.cs" />
diff --git a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.netcoreapp.cs b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.netcoreapp.cs
index cde0b3aebe735..6de1351b17e50 100644
--- a/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.netcoreapp.cs
+++ b/src/libraries/System.Security.Permissions/ref/System.Security.Permissions.netcoreapp.cs
@@ -6,6 +6,9 @@
 
 namespace System.Xaml.Permissions
 {
+#if NET50_OBSOLETIONS
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#endif
     public sealed partial class XamlLoadPermission : System.Security.CodeAccessPermission, System.Security.Permissions.IUnrestrictedPermission
     {
         public XamlLoadPermission(System.Collections.Generic.IEnumerable<System.Xaml.Permissions.XamlAccessLevel> allowedAccess) { }
diff --git a/src/libraries/System.Security.Permissions/src/System.Security.Permissions.csproj b/src/libraries/System.Security.Permissions/src/System.Security.Permissions.csproj
index ab56a608e193c..265879918e8cd 100644
--- a/src/libraries/System.Security.Permissions/src/System.Security.Permissions.csproj
+++ b/src/libraries/System.Security.Permissions/src/System.Security.Permissions.csproj
@@ -4,8 +4,9 @@
     <TargetFrameworks>$(NetCoreAppCurrent);netcoreapp3.0;netstandard2.0;net461;$(NetFrameworkCurrent)</TargetFrameworks>
     <ExcludeCurrentFullFrameworkFromPackage>true</ExcludeCurrentFullFrameworkFromPackage>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)'">
-    <DefineConstants>$(DefineConstants);CAS_OBSOLETIONS</DefineConstants>
+  <!-- We conditionally apply net5.0+ obsoletions -->
+  <PropertyGroup Condition="!($(TargetFramework.StartsWith('netcoreapp')) or $(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('net4')))">
+    <DefineConstants>$(DefineConstants);NET50_OBSOLETIONS</DefineConstants>
   </PropertyGroup>
   <ItemGroup Condition="!$(TargetFramework.StartsWith('net4'))">
     <Compile Include="System\ApplicationIdentity.cs" />
@@ -179,6 +180,8 @@
     <Compile Include="System\Web\AspNetHostingPermission.cs" />
     <Compile Include="System\Web\AspNetHostingPermissionAttribute.cs" />
     <Compile Include="System\Web\AspNetHostingPermissionLevel.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs"
+             Link="Common\System\Obsoletions.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFramework)' == '$(NetCoreAppCurrent)' or '$(TargetFramework)' == 'netcoreapp3.0'">
     <Compile Include="System\Xaml\Permissions\XamlLoadPermission.cs" />
diff --git a/src/libraries/System.Security.Permissions/src/System/Configuration/ConfigurationPermission.cs b/src/libraries/System.Security.Permissions/src/System/Configuration/ConfigurationPermission.cs
index 1a0875276b6c6..698fc4bcc1b97 100644
--- a/src/libraries/System.Security.Permissions/src/System/Configuration/ConfigurationPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Configuration/ConfigurationPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Configuration
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class ConfigurationPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public ConfigurationPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Data/Common/DBDataPermission.cs b/src/libraries/System.Security.Permissions/src/System/Data/Common/DBDataPermission.cs
index 74ecdb3d92aa9..d6d97f1aa61ce 100644
--- a/src/libraries/System.Security.Permissions/src/System/Data/Common/DBDataPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Data/Common/DBDataPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Data.Common
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public abstract class DBDataPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         protected DBDataPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Data/Odbc/OdbcPermission.cs b/src/libraries/System.Security.Permissions/src/System/Data/Odbc/OdbcPermission.cs
index 85b9664a479a5..34a7312b698c2 100644
--- a/src/libraries/System.Security.Permissions/src/System/Data/Odbc/OdbcPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Data/Odbc/OdbcPermission.cs
@@ -7,6 +7,9 @@
 
 namespace System.Data.Odbc
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class OdbcPermission : DBDataPermission
     {
         public OdbcPermission() : base(default(PermissionState)) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Data/OleDb/OleDbPermission.cs b/src/libraries/System.Security.Permissions/src/System/Data/OleDb/OleDbPermission.cs
index c55dce66b16b2..f5ccf474348d4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Data/OleDb/OleDbPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Data/OleDb/OleDbPermission.cs
@@ -7,6 +7,9 @@
 
 namespace System.Data.OleDb
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class OleDbPermission : DBDataPermission
     {
         public OleDbPermission() : base(default(PermissionState)) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Data/OracleClient/OraclePermission.cs b/src/libraries/System.Security.Permissions/src/System/Data/OracleClient/OraclePermission.cs
index 362f11ffdf3a9..e870d68d524e2 100644
--- a/src/libraries/System.Security.Permissions/src/System/Data/OracleClient/OraclePermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Data/OracleClient/OraclePermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Data.OracleClient
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class OraclePermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public OraclePermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Data/SqlClient/SqlClientPermission.cs b/src/libraries/System.Security.Permissions/src/System/Data/SqlClient/SqlClientPermission.cs
index fce107c83e2a6..694c7667c6b5c 100644
--- a/src/libraries/System.Security.Permissions/src/System/Data/SqlClient/SqlClientPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Data/SqlClient/SqlClientPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Data.SqlClient
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class SqlClientPermission : DBDataPermission
     {
         public SqlClientPermission() : base(default(PermissionState)) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Diagnostics/EventLogPermission.cs b/src/libraries/System.Security.Permissions/src/System/Diagnostics/EventLogPermission.cs
index ae89e63435b6a..3ed45ceb67133 100644
--- a/src/libraries/System.Security.Permissions/src/System/Diagnostics/EventLogPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Diagnostics/EventLogPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.Diagnostics
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class EventLogPermission : ResourcePermissionBase
     {
         public EventLogPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Diagnostics/PerformanceCounterPermission.cs b/src/libraries/System.Security.Permissions/src/System/Diagnostics/PerformanceCounterPermission.cs
index b50cead4b6846..3839ef63781d0 100644
--- a/src/libraries/System.Security.Permissions/src/System/Diagnostics/PerformanceCounterPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Diagnostics/PerformanceCounterPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.Diagnostics
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class PerformanceCounterPermission : ResourcePermissionBase
     {
         public PerformanceCounterPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Drawing/Printing/PrintingPermission.cs b/src/libraries/System.Security.Permissions/src/System/Drawing/Printing/PrintingPermission.cs
index 48de3038cbdaa..88c39a8df337e 100644
--- a/src/libraries/System.Security.Permissions/src/System/Drawing/Printing/PrintingPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Drawing/Printing/PrintingPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Drawing.Printing
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class PrintingPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public PrintingPermission(PrintingPermissionLevel printingLevel) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/DnsPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/DnsPermission.cs
index acfaeb32acf04..8440027071552 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/DnsPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/DnsPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class DnsPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public DnsPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/Mail/SmtpPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/Mail/SmtpPermission.cs
index 32419db6c8151..42fbd37022111 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/Mail/SmtpPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/Mail/SmtpPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net.Mail
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class SmtpPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public SmtpPermission(bool unrestricted) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/NetworkInformation/NetworkInformationPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/NetworkInformation/NetworkInformationPermission.cs
index a533d8234ec2e..9b44611e5ab2b 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/NetworkInformation/NetworkInformationPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/NetworkInformation/NetworkInformationPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net.NetworkInformation
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class NetworkInformationPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public NetworkInformationPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/Collaboration/PeerCollaborationPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/Collaboration/PeerCollaborationPermission.cs
index 96a54d4ced455..f43323a516f75 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/Collaboration/PeerCollaborationPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/Collaboration/PeerCollaborationPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net.PeerToPeer.Collaboration
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class PeerCollaborationPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public PeerCollaborationPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/PnrpPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/PnrpPermission.cs
index cc002543eca3c..fe5bbc5c5aaf0 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/PnrpPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/PeerToPeer/PnrpPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net.PeerToPeer
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class PnrpPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public PnrpPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/SocketPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/SocketPermission.cs
index d99a6746c672e..1ec9ec6cc0a05 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/SocketPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/SocketPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Net
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class SocketPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public const int AllPorts = -1;
diff --git a/src/libraries/System.Security.Permissions/src/System/Net/WebPermission.cs b/src/libraries/System.Security.Permissions/src/System/Net/WebPermission.cs
index 0ad404523320e..b09aa99a0816b 100644
--- a/src/libraries/System.Security.Permissions/src/System/Net/WebPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Net/WebPermission.cs
@@ -8,6 +8,9 @@
 
 namespace System.Net
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class WebPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public WebPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/HostProtectionException.cs b/src/libraries/System.Security.Permissions/src/System/Security/HostProtectionException.cs
index 04fdb6528b180..a6f292515de78 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/HostProtectionException.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/HostProtectionException.cs
@@ -7,6 +7,9 @@
 
 namespace System.Security
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Serializable]
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
     public partial class HostProtectionException : SystemException
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermission.cs
index 8f9b34f0b6f85..0742f9322666f 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class DataProtectionPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public DataProtectionPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionAttribute.cs
index a78faa3fc3fde..e746711b82e9f 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class
      | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false )]
     public sealed class DataProtectionPermissionAttribute : CodeAccessSecurityAttribute
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionFlags.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionFlags.cs
index c057296ee153d..f0d525b3caa2b 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionFlags.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/DataProtectionPermissionFlags.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum DataProtectionPermissionFlags
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermission.cs
index 40c1f216633af..573b37eb083cd 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class EnvironmentPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public EnvironmentPermission(EnvironmentPermissionAccess flag, string pathList) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAccess.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAccess.cs
index 44a757a007c9d..6ec356bd68b4a 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAccess.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAccess.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum EnvironmentPermissionAccess
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAttribute.cs
index fdb27ad7bfeb9..a7998d5f06759 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/EnvironmentPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class EnvironmentPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermission.cs
index 6f8c3744fd52d..c63ed9494407f 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class FileDialogPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public FileDialogPermission(FileDialogPermissionAccess access) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAccess.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAccess.cs
index d1419bd4cc8d6..2e185c7826d39 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAccess.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAccess.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum FileDialogPermissionAccess
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAttribute.cs
index 065d3701f5f0e..d1b6160c55cf2 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileDialogPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class FileDialogPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermission.cs
index 60797f4dc553d..254efa3e8def4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class FileIOPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public FileIOPermission(FileIOPermissionAccess access, string path) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAccess.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAccess.cs
index d1301d4869e18..b37d2dcfee84c 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAccess.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAccess.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum FileIOPermissionAccess
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAttribute.cs
index e64b0cf1e89d6..bbbf4eb4ccb69 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/FileIOPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class FileIOPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermission.cs
index dd7540489ff9a..7f2daee154caf 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class GacIdentityPermission : CodeAccessPermission
     {
         public GacIdentityPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermissionAttribute.cs
index cdf3ec139b087..716728e28c618 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/GacIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class GacIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionAttribute.cs
index adf3a3f784bba..2c5fc1eecd695 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(4205), AllowMultiple = true, Inherited = false)]
     public sealed partial class HostProtectionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionResource.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionResource.cs
index 25381f2977524..312a6ce421a0e 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionResource.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/HostProtectionResource.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     [System.Runtime.CompilerServices.TypeForwardedFrom("mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089")]
     public enum HostProtectionResource
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IUnrestrictedPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IUnrestrictedPermission.cs
index 2262f51a168f1..cad91be9b17ea 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IUnrestrictedPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IUnrestrictedPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public partial interface IUnrestrictedPermission
     {
         bool IsUnrestricted();
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageContainment.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageContainment.cs
index 6e97b04baedf0..eb6bd1cc2009d 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageContainment.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageContainment.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum IsolatedStorageContainment
     {
         None = 0x00,
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermission.cs
index 72185df65bb18..755b25dac3a88 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class IsolatedStorageFilePermission : IsolatedStoragePermission
     {
         public IsolatedStorageFilePermission(PermissionState state) : base(state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermissionAttribute.cs
index 402190168c2ee..f103e65a51ce5 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStorageFilePermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor
      | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly,
     AllowMultiple = true, Inherited = false)]
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermission.cs
index 71f149e73c17e..b0d9cc541aa85 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public abstract class IsolatedStoragePermission : CodeAccessPermission, IUnrestrictedPermission
     {
         protected IsolatedStoragePermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermissionAttribute.cs
index 0afa27332214f..254d193a4f3a8 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/IsolatedStoragePermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public abstract class IsolatedStoragePermissionAttribute : CodeAccessSecurityAttribute
     {
         protected IsolatedStoragePermissionAttribute(SecurityAction action) : base(action) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermission.cs
index 05e33c0a183b0..eb4e5f96d2ced 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class KeyContainerPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public KeyContainerPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntry.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntry.cs
index 836105c919af2..6a7de830a9e7f 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntry.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntry.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class KeyContainerPermissionAccessEntry
     {
         public KeyContainerPermissionAccessEntry(string keyContainerName, KeyContainerPermissionFlags flags) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryCollection.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryCollection.cs
index 7e34685573087..37362d255bdf4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryCollection.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryCollection.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class KeyContainerPermissionAccessEntryCollection : ICollection
     {
         public KeyContainerPermissionAccessEntry this[int index] { get { return null; } }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryEnumerator.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryEnumerator.cs
index fbacdefd855c0..453352a458668 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryEnumerator.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAccessEntryEnumerator.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class KeyContainerPermissionAccessEntryEnumerator : IEnumerator
     {
         public KeyContainerPermissionAccessEntry Current { get; }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAttribute.cs
index 31021ac3d121b..a80318df0691b 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class KeyContainerPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionFlags.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionFlags.cs
index a802cb5f55594..c6ec636045582 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionFlags.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/KeyContainerPermissionFlags.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum KeyContainerPermissionFlags
     {
         NoFlags = 0x0000,
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/MediaPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/MediaPermission.cs
index 8126aaf3b92b6..e1112f09eb0cb 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/MediaPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/MediaPermission.cs
@@ -2,6 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum MediaPermissionAudio
     {
         NoAudio,
@@ -9,6 +12,10 @@ public enum MediaPermissionAudio
         SafeAudio,
         AllAudio
     }
+
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum MediaPermissionVideo
     {
         NoVideo,
@@ -16,6 +23,10 @@ public enum MediaPermissionVideo
         SafeVideo,
         AllVideo,
     }
+
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum MediaPermissionImage
     {
         NoImage,
@@ -23,6 +34,10 @@ public enum MediaPermissionImage
         SafeImage,
         AllImage,
     }
+
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class MediaPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public MediaPermission() { }
@@ -45,6 +60,10 @@ public override void FromXml(SecurityElement securityElement) { }
         public MediaPermissionVideo Video { get { return MediaPermissionVideo.AllVideo; } }
         public MediaPermissionImage Image { get { return MediaPermissionImage.AllImage; } }
     }
+
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class MediaPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PermissionSetAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PermissionSetAttribute.cs
index 1d32c7e66a1f8..a03d56df74547 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PermissionSetAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PermissionSetAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class PermissionSetAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermission.cs
index e11b21b06365f..c1379d1c431ff 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermission.cs
@@ -8,6 +8,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class PrincipalPermission : IPermission, ISecurityEncodable, IUnrestrictedPermission
     {
         private IDRole[] _idArray;
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermissionAttribute.cs
index 8cbc85a84c0ef..6d90b43d563f5 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PrincipalPermissionAttribute.cs
@@ -3,11 +3,14 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(68), AllowMultiple = true, Inherited = false)]
     public sealed partial class PrincipalPermissionAttribute : CodeAccessSecurityAttribute
     {
-#if CAS_OBSOLETIONS
-        [Obsolete("PrincipalPermissionAttribute is not honored by the runtime and must not be used.", error: true, DiagnosticId = "MSLIB0002", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+#if NET50_OBSOLETIONS
+        [Obsolete(Obsoletions.PrincipalPermissionAttributeMessage, error: true, DiagnosticId = Obsoletions.PrincipalPermissionAttributeDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
 #endif
         public PrincipalPermissionAttribute(SecurityAction action) : base(default(SecurityAction)) { }
         public bool Authenticated { get; set; }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermission.cs
index 45fc03dbe9f4b..ce5a5aaf4a74d 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class PublisherIdentityPermission : CodeAccessPermission
     {
         public PublisherIdentityPermission(X509Certificate certificate) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermissionAttribute.cs
index 66c4420ac03d7..83472181db343 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/PublisherIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class PublisherIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermission.cs
index bd10192393de9..e2bc2ba597341 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class ReflectionPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public ReflectionPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionAttribute.cs
index b023a7d407acb..e478f8f7100f7 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class ReflectionPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionFlag.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionFlag.cs
index 4cba9c4500cb6..8167e26a71895 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionFlag.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ReflectionPermissionFlag.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum ReflectionPermissionFlag
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermission.cs
index 6b0b3a8c13628..5faae9f269938 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class RegistryPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public RegistryPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAccess.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAccess.cs
index 6b675e6b64e94..94d78a164a3f4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAccess.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAccess.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum RegistryPermissionAccess
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAttribute.cs
index 0d6f101d72fb3..9665d5e054065 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/RegistryPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class RegistryPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBase.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBase.cs
index 95dd1b13bd803..cab8d9d00d4e7 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBase.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBase.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public abstract class ResourcePermissionBase : CodeAccessPermission, IUnrestrictedPermission
     {
         public const string Any = "*";
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBaseEntry.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBaseEntry.cs
index c43dd1999db5f..4ad9984f203fb 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBaseEntry.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ResourcePermissionBaseEntry.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public class ResourcePermissionBaseEntry
     {
         public ResourcePermissionBaseEntry() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SecurityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SecurityPermission.cs
index 7365d1d4c8cf9..feb082ac71a2a 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SecurityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SecurityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class SecurityPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public SecurityPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermission.cs
index f73347b7f759e..9969587efdf55 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class SiteIdentityPermission : CodeAccessPermission
     {
         public SiteIdentityPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermissionAttribute.cs
index 2c43621aeed8f..e01e27f631a52 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/SiteIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class SiteIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermission.cs
index 773cbdeb8ff6e..c99b7d7528368 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class StorePermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public StorePermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionAttribute.cs
index 6fb9a77b3119c..29191d870412e 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class StorePermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionFlags.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionFlags.cs
index aeaa0453a9224..5d10d3bf11735 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionFlags.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StorePermissionFlags.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum StorePermissionFlags
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermission.cs
index d3cb3c41ef2dc..4c828380ab0fc 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class StrongNameIdentityPermission : CodeAccessPermission
     {
         public StrongNameIdentityPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermissionAttribute.cs
index 7482738ea1253..d631f897ce482 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNameIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class StrongNameIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNamePublicKeyBlob.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNamePublicKeyBlob.cs
index 78ce7318851e7..14f7fc8299e73 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNamePublicKeyBlob.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/StrongNamePublicKeyBlob.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class StrongNamePublicKeyBlob
     {
         public StrongNamePublicKeyBlob(byte[] publicKey) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermission.cs
index 94db9d0f4ccbd..8dad856297c05 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class TypeDescriptorPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public TypeDescriptorPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionAttribute.cs
index 35a4a4ba130ec..107f99a74e867 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class TypeDescriptorPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionFlags.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionFlags.cs
index 77af90048313d..fb137fd5e820b 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionFlags.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/TypeDescriptorPermissionFlags.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [Flags]
     public enum TypeDescriptorPermissionFlags
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermission.cs
index a39b5cf5118e7..ce45a21463886 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class UIPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public UIPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionAttribute.cs
index c178e631942c9..bd53734c3f4eb 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class UIPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionClipboard.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionClipboard.cs
index d094e3b1fc026..e6d08e6d951fb 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionClipboard.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionClipboard.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum UIPermissionClipboard
     {
         AllClipboard = 2,
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionWindow.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionWindow.cs
index 469bc4a3ba3af..8611c8bae0c1c 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionWindow.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UIPermissionWindow.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum UIPermissionWindow
     {
         AllWindows = 3,
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermission.cs
index 0c9c76e7b1acb..8b828ab9877af 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class UrlIdentityPermission : CodeAccessPermission
     {
         public UrlIdentityPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermissionAttribute.cs
index 6190536cf4ba7..a80aca35574a4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/UrlIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class UrlIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/WebBrowserPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/WebBrowserPermission.cs
index 03611429ac21a..1fc5a73aa5bc4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/WebBrowserPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/WebBrowserPermission.cs
@@ -2,12 +2,19 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public enum WebBrowserPermissionLevel
     {
         None,
         Safe,
         Unrestricted
     }
+
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class WebBrowserPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public WebBrowserPermission() { }
@@ -23,6 +30,9 @@ public override void FromXml(SecurityElement securityElement) { }
         public WebBrowserPermissionLevel Level { get { return WebBrowserPermissionLevel.Unrestricted; } set { } }
     }
 
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
     public sealed class WebBrowserPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermission.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermission.cs
index c27ee912baef3..4768866e96ad4 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermission.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class ZoneIdentityPermission : CodeAccessPermission
     {
         public ZoneIdentityPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermissionAttribute.cs b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermissionAttribute.cs
index b9bf61fbf5ede..ab60bb08023c5 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermissionAttribute.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Permissions/ZoneIdentityPermissionAttribute.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     [AttributeUsage((AttributeTargets)(109), AllowMultiple = true, Inherited = false)]
     public sealed partial class ZoneIdentityPermissionAttribute : CodeAccessSecurityAttribute
     {
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Policy/ApplicationTrust.cs b/src/libraries/System.Security.Permissions/src/System/Security/Policy/ApplicationTrust.cs
index bffdd9364bcc8..834d129d35f22 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Policy/ApplicationTrust.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Policy/ApplicationTrust.cs
@@ -9,10 +9,16 @@ public sealed partial class ApplicationTrust : EvidenceBase, ISecurityEncodable
     {
         public ApplicationTrust() { }
         public ApplicationTrust(ApplicationIdentity identity) { }
+#if NET50_OBSOLETIONS
+        [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
         public ApplicationTrust(PermissionSet defaultGrantSet, IEnumerable<StrongName> fullTrustAssemblies) { }
         public ApplicationIdentity ApplicationIdentity { get; set; }
         public PolicyStatement DefaultGrantSet { get; set; }
         public object ExtraInfo { get; set; }
+#if NET50_OBSOLETIONS
+        [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
         public IList<StrongName> FullTrustAssemblies { get { return default(IList<StrongName>); } }
         public bool IsApplicationTrustedToRun { get; set; }
         public bool Persist { get; set; }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Policy/FileCodeGroup.cs b/src/libraries/System.Security.Permissions/src/System/Security/Policy/FileCodeGroup.cs
index 1c5b2c3511652..085dea2050429 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Policy/FileCodeGroup.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Policy/FileCodeGroup.cs
@@ -3,6 +3,9 @@
 
 namespace System.Security.Policy
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class FileCodeGroup : CodeGroup
     {
         public FileCodeGroup(IMembershipCondition membershipCondition, Permissions.FileIOPermissionAccess access) : base(default(IMembershipCondition), default(PolicyStatement)) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongName.cs b/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongName.cs
index d2b5b98da6430..69c1c87bfadcc 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongName.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongName.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Policy
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class StrongName : EvidenceBase, IIdentityPermissionFactory
     {
         public StrongName(StrongNamePublicKeyBlob blob, string name, Version version) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongNameMembershipCondition.cs b/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongNameMembershipCondition.cs
index 7c5289e6e1864..31a5a5adc7113 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongNameMembershipCondition.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/Policy/StrongNameMembershipCondition.cs
@@ -5,6 +5,9 @@
 
 namespace System.Security.Policy
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed partial class StrongNameMembershipCondition : ISecurityEncodable, ISecurityPolicyEncodable, IMembershipCondition
     {
         public StrongNameMembershipCondition(StrongNamePublicKeyBlob blob, string name, Version version) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Security/SecurityManager.cs b/src/libraries/System.Security.Permissions/src/System/Security/SecurityManager.cs
index b08cd1c50e498..90377ad669e34 100644
--- a/src/libraries/System.Security.Permissions/src/System/Security/SecurityManager.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Security/SecurityManager.cs
@@ -6,6 +6,9 @@
 
 namespace System.Security
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public static partial class SecurityManager
     {
         [Obsolete]
diff --git a/src/libraries/System.Security.Permissions/src/System/ServiceProcess/ServiceControllerPermission.cs b/src/libraries/System.Security.Permissions/src/System/ServiceProcess/ServiceControllerPermission.cs
index 462dbd40f2b9a..d98493b03d7e4 100644
--- a/src/libraries/System.Security.Permissions/src/System/ServiceProcess/ServiceControllerPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/ServiceProcess/ServiceControllerPermission.cs
@@ -5,6 +5,9 @@
 
 namespace System.ServiceProcess
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class ServiceControllerPermission : ResourcePermissionBase
     {
         public ServiceControllerPermission() { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Transactions/DistributedTransactionPermission.cs b/src/libraries/System.Security.Permissions/src/System/Transactions/DistributedTransactionPermission.cs
index 2af2f6e243021..3d797f7934700 100644
--- a/src/libraries/System.Security.Permissions/src/System/Transactions/DistributedTransactionPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Transactions/DistributedTransactionPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Transactions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class DistributedTransactionPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public DistributedTransactionPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Web/AspNetHostingPermission.cs b/src/libraries/System.Security.Permissions/src/System/Web/AspNetHostingPermission.cs
index 87b203d4afee4..e4e7ac739c8cf 100644
--- a/src/libraries/System.Security.Permissions/src/System/Web/AspNetHostingPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Web/AspNetHostingPermission.cs
@@ -6,6 +6,9 @@
 
 namespace System.Web
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class AspNetHostingPermission :  CodeAccessPermission, IUnrestrictedPermission
     {
         public AspNetHostingPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/src/System/Xaml/Permissions/XamlLoadPermission.cs b/src/libraries/System.Security.Permissions/src/System/Xaml/Permissions/XamlLoadPermission.cs
index c4d74e5062a04..12e7abe0a0f25 100644
--- a/src/libraries/System.Security.Permissions/src/System/Xaml/Permissions/XamlLoadPermission.cs
+++ b/src/libraries/System.Security.Permissions/src/System/Xaml/Permissions/XamlLoadPermission.cs
@@ -9,6 +9,9 @@
 
 namespace System.Xaml.Permissions
 {
+#if NET50_OBSOLETIONS
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
+#endif
     public sealed class XamlLoadPermission : CodeAccessPermission, IUnrestrictedPermission
     {
         public XamlLoadPermission(PermissionState state) { }
diff --git a/src/libraries/System.Security.Permissions/tests/System.Security.Permissions.Tests.csproj b/src/libraries/System.Security.Permissions/tests/System.Security.Permissions.Tests.csproj
index e6c10c1d6ae29..2097721d5d4f2 100644
--- a/src/libraries/System.Security.Permissions/tests/System.Security.Permissions.Tests.csproj
+++ b/src/libraries/System.Security.Permissions/tests/System.Security.Permissions.Tests.csproj
@@ -1,6 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+    <!-- SYSLIB0003 is the obsoletion of CAS, but we still have unit tests for it -->
+    <NoWarn>$(NoWarn);SYSLIB0003</NoWarn>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="ApplicationTrustTests.cs" />
diff --git a/src/libraries/System.Text.Encoding.Extensions/ref/System.Text.Encoding.Extensions.cs b/src/libraries/System.Text.Encoding.Extensions/ref/System.Text.Encoding.Extensions.cs
index c7ad11255819e..834158f0b94c0 100644
--- a/src/libraries/System.Text.Encoding.Extensions/ref/System.Text.Encoding.Extensions.cs
+++ b/src/libraries/System.Text.Encoding.Extensions/ref/System.Text.Encoding.Extensions.cs
@@ -95,9 +95,9 @@ public UTF32Encoding(bool bigEndian, bool byteOrderMark, bool throwOnInvalidChar
     }
     public partial class UTF7Encoding : System.Text.Encoding
     {
-        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "MSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "SYSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public UTF7Encoding() { }
-        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "MSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
+        [System.ObsoleteAttribute("The UTF-7 encoding is insecure and should not be used. Consider using UTF-8 instead.", DiagnosticId = "SYSLIB0001", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public UTF7Encoding(bool allowOptionals) { }
         public override bool Equals(object? value) { throw null; }
         [System.CLSCompliantAttribute(false)]
diff --git a/src/libraries/System.Text.Encoding/tests/System.Text.Encoding.Tests.csproj b/src/libraries/System.Text.Encoding/tests/System.Text.Encoding.Tests.csproj
index f4077aa49f273..78c22e0243c91 100644
--- a/src/libraries/System.Text.Encoding/tests/System.Text.Encoding.Tests.csproj
+++ b/src/libraries/System.Text.Encoding/tests/System.Text.Encoding.Tests.csproj
@@ -5,7 +5,7 @@
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
     <!-- Encoding.UTF7 and UTF7Encoding are obsolete, but we're the unit test project for it, so suppress warnings -->
-    <NoWarn>$(NoWarn),MSLIB0001</NoWarn>
+    <NoWarn>$(NoWarn),SYSLIB0001</NoWarn>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="ASCIIEncoding\ASCIIEncodingEncode.cs" />
diff --git a/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.cs b/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.cs
index 142afdea8ec2a..83df550d43ddb 100644
--- a/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.cs
+++ b/src/libraries/System.Threading.Thread/ref/System.Threading.Thread.cs
@@ -50,7 +50,9 @@ public Thread(System.Threading.ThreadStart start, int maxStackSize) { }
         public string? Name { get { throw null; } set { } }
         public System.Threading.ThreadPriority Priority { get { throw null; } set { } }
         public System.Threading.ThreadState ThreadState { get { throw null; } }
+        [System.ObsoleteAttribute("Thread.Abort is not supported and throws PlatformNotSupportedException.", DiagnosticId = "SYSLIB0006", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public void Abort() { }
+        [System.ObsoleteAttribute("Thread.Abort is not supported and throws PlatformNotSupportedException.", DiagnosticId = "SYSLIB0006", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public void Abort(object? stateInfo) { }
         public static System.LocalDataStoreSlot AllocateDataSlot() { throw null; }
         public static System.LocalDataStoreSlot AllocateNamedDataSlot(string name) { throw null; }
diff --git a/src/libraries/System.Threading.Thread/tests/ThreadTests.cs b/src/libraries/System.Threading.Thread/tests/ThreadTests.cs
index 55a53c8ebfd55..443c500fd8e80 100644
--- a/src/libraries/System.Threading.Thread/tests/ThreadTests.cs
+++ b/src/libraries/System.Threading.Thread/tests/ThreadTests.cs
@@ -731,12 +731,12 @@ public static void AbortSuspendTest()
 
             Action verify = () =>
             {
+#pragma warning disable SYSLIB0006, 618 // Obsolete: Abort, Suspend, Resume
                 Assert.Throws<PlatformNotSupportedException>(() => t.Abort());
                 Assert.Throws<PlatformNotSupportedException>(() => t.Abort(t));
-#pragma warning disable 618 // Obsolete members
                 Assert.Throws<PlatformNotSupportedException>(() => t.Suspend());
                 Assert.Throws<PlatformNotSupportedException>(() => t.Resume());
-#pragma warning restore 618 // Obsolete members
+#pragma warning restore SYSLIB0006, 618 // Obsolete: Abort, Suspend, Resume
             };
             verify();
 
diff --git a/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.Mono.cs b/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.Mono.cs
index 3ae5512e121db..feedd6aded355 100644
--- a/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.Mono.cs
+++ b/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/Emit/AssemblyBuilder.Mono.cs
@@ -551,6 +551,7 @@ public override Module ManifestModule
             }
         }
 
+        [Obsolete(Obsoletions.GlobalAssemblyCacheMessage, DiagnosticId = Obsoletions.GlobalAssemblyCacheDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public override bool GlobalAssemblyCache
         {
             get
diff --git a/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs b/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
index 50814ab8297bd..e1f386a4d2eae 100644
--- a/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
+++ b/src/mono/netcore/System.Private.CoreLib/src/System/Reflection/RuntimeAssembly.cs
@@ -107,6 +107,7 @@ public override event ModuleResolveEventHandler? ModuleResolve
 
         public override Module ManifestModule => GetManifestModuleInternal();
 
+        [Obsolete(Obsoletions.GlobalAssemblyCacheMessage, DiagnosticId = Obsoletions.GlobalAssemblyCacheDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public override bool GlobalAssemblyCache => false;
 
         public override long HostContext => 0;