BinaryFormatter deprecation for System.Configuration.ConfigurationManager

src/libraries/System.Configuration.ConfigurationManager/ref/System.Configuration.ConfigurationManager.cs

@@ -1213,6 +1213,7 @@ public enum SettingsSerializeAs
     {
         String = 0,
         Xml = 1,
+        [System.ObsoleteAttribute(System.Obsoletions.BinaryFormatterMessage + @". Consider using Xml instead.", false)]
         Binary = 2,
         ProviderSpecific = 3,
     }

src/libraries/System.Configuration.ConfigurationManager/ref/System.Configuration.ConfigurationManager.csproj

@@ -9,6 +9,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.Configuration.ConfigurationManager.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs" Link="Common\System\Obsoletions.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\System.Security.Permissions\ref\System.Security.Permissions.csproj" />

src/libraries/System.Configuration.ConfigurationManager/src/System.Configuration.ConfigurationManager.csproj

@@ -248,6 +248,7 @@
     <Compile Include="System\UriIdnScope.cs" />
     <Compile Include="$(CommonPath)System\IO\TempFileCollection.cs"
              Link="Common\System\IO\TempFileCollection.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs" Link="Common\System\Obsoletions.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(IsPartialFacadeAssembly)' != 'true'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Cryptography.ProtectedData\src\System.Security.Cryptography.ProtectedData.csproj" />

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/LocalFileSettingsProvider.cs

@@ -462,7 +462,9 @@ private XmlNode SerializeToXmlElement(SettingsProperty setting, SettingsProperty
 
             string serializedValue = value.SerializedValue as string;
 
+#pragma warning disable CS0618 // Type or member is obsolete
             if (serializedValue == null && setting.SerializeAs == SettingsSerializeAs.Binary)
+#pragma warning restore CS0618 // Type or member is obsolete
             {
                 // SettingsPropertyValue returns a byte[] in the binary serialization case. We need to
                 // encode this - we use base64 since SettingsPropertyValue understands it and we won't have

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/SettingsProperty.cs

@@ -5,6 +5,8 @@ namespace System.Configuration
 {
     public class SettingsProperty
     {
+        internal static bool EnableUnsafeBinaryFormatterInPropertyValueSerialization { get; } = AppContext.TryGetSwitch("System.Configuration.ConfigurationManager.EnableUnsafeBinaryFormatterInPropertyValueSerialization", out bool isEnabled) ? isEnabled : false;
+
         public virtual string Name { get; set; }
         public virtual bool IsReadOnly { get; set; }
         public virtual object DefaultValue { get; set; }
@@ -37,7 +39,19 @@ public SettingsProperty(
             Provider = provider;
             IsReadOnly = isReadOnly;
             DefaultValue = defaultValue;
-            SerializeAs = serializeAs;
+#pragma warning disable CS0618 // Type or member is obsolete
+            if (serializeAs == SettingsSerializeAs.Binary)
+#pragma warning restore CS0618 // Type or member is obsolete
+            {
+                if (EnableUnsafeBinaryFormatterInPropertyValueSerialization)
+                {
+                    SerializeAs = serializeAs;
+                }
+                else
+                {
+                    throw new NotSupportedException(Obsoletions.BinaryFormatterMessage);
+                }
+            }
             Attributes = attributes;
             ThrowOnErrorDeserializing = throwOnErrorDeserializing;
             ThrowOnErrorSerializing = throwOnErrorSerializing;

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/SettingsPropertyValue.cs

@@ -88,6 +88,7 @@ private object Deserialize()
             // Attempt 1: Try creating from SerializedValue
             if (SerializedValue != null)
             {
+                bool throwBinaryFormatterDeprecationException = false;
                 try
                 {
                     if (SerializedValue is string)
@@ -96,10 +97,17 @@ private object Deserialize()
                     }
                     else
                     {
-                        using (MemoryStream ms = new MemoryStream((byte[])SerializedValue))
+                        // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
+                        if (SettingsProperty.EnableUnsafeBinaryFormatterInPropertyValueSerialization)
                         {
-                            // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
-                            value = (new BinaryFormatter()).Deserialize(ms);
+                            using (MemoryStream ms = new MemoryStream((byte[])SerializedValue))
+                            {
+                                value = (new BinaryFormatter()).Deserialize(ms);
+                            }
+                        }
+                        else
+                        {
+                            throwBinaryFormatterDeprecationException = true;
                         }
                     }
                 }
@@ -124,6 +132,11 @@ private object Deserialize()
                     }
                 }
 
+                if (throwBinaryFormatterDeprecationException)
+                {
+                    throw new NotSupportedException(Obsoletions.BinaryFormatterMessage);
+                }
+
                 if (value != null && !Property.PropertyType.IsAssignableFrom(value.GetType())) // is it the correct type
                     value = null;
             }
@@ -192,12 +205,21 @@ private static object GetObjectFromString(Type type, SettingsSerializeAs seriali
             // Convert based on the serialized type
             switch (serializeAs)
             {
+#pragma warning disable CS0618 // Type or member is obsolete
                 case SettingsSerializeAs.Binary:
-                    byte[] buffer = Convert.FromBase64String(serializedValue);
-                    using (MemoryStream ms = new MemoryStream(buffer))
+#pragma warning restore CS0618 // Type or member is obsolete
+                    if (SettingsProperty.EnableUnsafeBinaryFormatterInPropertyValueSerialization)
                     {
-                        // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
-                        return (new BinaryFormatter()).Deserialize(ms);
+                        byte[] buffer = Convert.FromBase64String(serializedValue);
+                        using (MemoryStream ms = new MemoryStream(buffer))
+                        {
+                            // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
+                            return (new BinaryFormatter()).Deserialize(ms);
+                        }
+                    }
+                    else
+                    {
+                        throw new NotSupportedException(Obsoletions.BinaryFormatterMessage);
                     }
                 case SettingsSerializeAs.Xml:
                     StringReader sr = new StringReader(serializedValue);
@@ -218,15 +240,26 @@ private object SerializePropertyValue()
             if (_value == null)
                 return null;
 
+#pragma warning disable CS0618 // Type or member is obsolete
             if (Property.SerializeAs != SettingsSerializeAs.Binary)
+#pragma warning restore CS0618 // Type or member is obsolete
+            {
                 return ConvertObjectToString(_value, Property.PropertyType, Property.SerializeAs, Property.ThrowOnErrorSerializing);
+            }
 
-            using (MemoryStream ms = new MemoryStream())
+            if (SettingsProperty.EnableUnsafeBinaryFormatterInPropertyValueSerialization)
+            {
+                using (MemoryStream ms = new MemoryStream())
+                {
+                    BinaryFormatter bf = new BinaryFormatter();
+                    // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
+                    bf.Serialize(ms, _value);
+                    return ms.ToArray();
+                }
+            }
+            else
             {
-                // Issue https://github.com/dotnet/runtime/issues/39295 tracks finding an alternative to BinaryFormatter
-                BinaryFormatter bf = new BinaryFormatter();
-                bf.Serialize(ms, _value);
-                return ms.ToArray();
+                throw new NotSupportedException(Obsoletions.BinaryFormatterMessage);
             }
         }
 
@@ -255,7 +288,9 @@ private static string ConvertObjectToString(object propertyValue, Type type, Set
 
                         xs.Serialize(sw, propertyValue);
                         return sw.ToString();
+#pragma warning disable CS0618 // Type or member is obsolete
                     case SettingsSerializeAs.Binary:
+#pragma warning restore CS0618 // Type or member is obsolete
                         Debug.Fail("Should not have gotten here with Binary formatting");
                         break;
                 }

src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/SettingsSerializeAs.cs

@@ -1,12 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
+
 namespace System.Configuration
 {
     public enum SettingsSerializeAs
     {
         String = 0,
         Xml = 1,
+        [Obsolete(Obsoletions.BinaryFormatterMessage + @". Consider using Xml instead.", false)]
         Binary = 2,
         ProviderSpecific = 3
     }

src/libraries/System.Configuration.ConfigurationManager/tests/System.Configuration.ConfigurationManager.Tests.csproj

@@ -61,6 +61,7 @@
     <Compile Include="System\Configuration\ApplicationSettingsBaseTests.cs" />
     <Compile Include="System\Configuration\AppSettingsReaderTests.cs" />
     <Compile Include="System\Configuration\AppSettingsTests.cs" />
+    <Compile Include="System\Configuration\BinaryFormatterDeprecationTests.cs" />
     <Compile Include="System\Configuration\CallBackValidatorAttributeTests.cs" />
     <Compile Include="System\Configuration\ConfigPathUtilityTests.cs" />
     <Compile Include="System\Configuration\ConfigurationElementCollectionTests.cs" />

src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/ApplicationSettingsBaseTests.cs

@@ -213,7 +213,9 @@ public void Reload_SimpleSettings_Ok()
         [ReadOnly(false)]
         [SettingsGroupName("TestGroup")]
         [SettingsProvider(typeof(TestProvider))]
+#pragma warning disable CS0618 // Type or member is obsolete
         [SettingsSerializeAs(SettingsSerializeAs.Binary)]
+#pragma warning restore CS0618 // Type or member is obsolete
         private class SettingsWithAttributes : ApplicationSettingsBase
         {
             [ApplicationScopedSetting]
@@ -243,7 +245,9 @@ public void SettingsProperty_SettingsWithAttributes_Ok()
             Assert.Equal(1, settings.Properties.Count);
             SettingsProperty property = settings.Properties["StringProperty"];
             Assert.Equal(typeof(TestProvider), property.Provider.GetType());
+#pragma warning disable CS0618 // Type or member is obsolete
             Assert.Equal(SettingsSerializeAs.Binary, property.SerializeAs);
+#pragma warning restore CS0618 // Type or member is obsolete
         }
 
         [Fact]

src/libraries/System.Configuration.ConfigurationManager/tests/System/Configuration/BinaryFormatterDeprecationTests.cs

@@ -0,0 +1,44 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Configuration;
+using Microsoft.DotNet.RemoteExecutor;
+using Xunit;
+
+namespace System.ConfigurationTests
+{
+    public class BinaryFormatterDeprecationTests
+    {
+        private static bool AreBinaryFormatterAndRemoteExecutorSupportedOnThisPlatform => PlatformDetection.IsBinaryFormatterSupported && RemoteExecutor.IsSupported;
+
+        [SkipOnTargetFramework(TargetFrameworkMonikers.NetFramework, "SettingsSerializeAs.Binary is deprecated only on Core")]
+        [Fact]
+        public void ThrowOnSettingsPropertyConstructorWithSettingsSerializeAsBinary()
+        {
+#pragma warning disable CS0618 // Type or member is obsolete
+            Assert.Throws<NotSupportedException>(() => new SettingsProperty("Binary", typeof(byte[]), null, false,"AString", SettingsSerializeAs.Binary, new SettingsAttributeDictionary(), true, true));
+#pragma warning restore CS0618 // Type or member is obsolete
+        }
+
+        [ConditionalFact(nameof(AreBinaryFormatterAndRemoteExecutorSupportedOnThisPlatform))]
+        public void SerializeAndDeserializeWithSettingsSerializeAsBinary()
+        {
+            RemoteInvokeOptions options = new RemoteInvokeOptions();
+            options.RuntimeConfigurationOptions.Add("System.Configuration.ConfigurationManager.EnableUnsafeBinaryFormatterInPropertyValueSerialization", bool.TrueString);
+            RemoteExecutor.Invoke(() =>
+            {
+#pragma warning disable CS0618 // Type or member is obsolete
+                SettingsProperty property = new SettingsProperty("Binary", typeof(string), null, false, "AString", SettingsSerializeAs.Binary, new SettingsAttributeDictionary(), true, true);
+#pragma warning restore CS0618 // Type or member is obsolete
+                SettingsPropertyValue value = new SettingsPropertyValue(property);
+                value.PropertyValue = "AString"; // To force _changedSinceLastSerialized to true to allow for serialization in the next call
+                object serializedValue = value.SerializedValue;
+                Assert.NotNull(serializedValue);
+                value.Deserialized = false;
+                object deserializedValue = value.PropertyValue;
+                Assert.Equal("AString", deserializedValue);
+            }, options).Dispose();
+        }
+    }
+}