[browser][wasm] Configuring request options in Browser WebAssembly

src/libraries/System.Net.Http/ref/System.Net.Http.cs

@@ -213,12 +213,22 @@ public HttpRequestMessage(System.Net.Http.HttpMethod method, System.Uri? request
         public System.Net.Http.Headers.HttpRequestHeaders Headers { get { throw null; } }
         public System.Net.Http.HttpMethod Method { get { throw null; } set { } }
         public System.Collections.Generic.IDictionary<string, object?> Properties { get { throw null; } }
+        public HttpRequestOptions Options { get { throw null; } }
         public System.Uri? RequestUri { get { throw null; } set { } }
         public System.Version Version { get { throw null; } set { } }
         public void Dispose() { }
         protected virtual void Dispose(bool disposing) { }
         public override string ToString() { throw null; }
     }
+
+    public readonly struct HttpRequestOptionsKey<TValue>
+    {
+        public HttpRequestOptionsKey(string key) {}
+        public string Key { get { throw null; } }
+    }
+
+    public sealed class HttpRequestOptions : System.Collections.Generic.Dictionary<string, object> { }
+
     public partial class HttpResponseMessage : System.IDisposable
     {
         public HttpResponseMessage() { }

src/libraries/System.Net.Http/src/System.Net.Http.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <AssemblyName>System.Net.Http</AssemblyName>
@@ -47,6 +47,8 @@
     <Compile Include="System\Net\Http\HttpParseResult.cs" />
     <Compile Include="System\Net\Http\HttpRequestException.cs" />
     <Compile Include="System\Net\Http\HttpRequestMessage.cs" />
+    <Compile Include="System\Net\Http\HttpRequestOptions.cs" />
+    <Compile Include="System\Net\Http\HttpRequestOptionsKey.cs" />
     <Compile Include="System\Net\Http\HttpResponseMessage.cs" />
     <Compile Include="System\Net\Http\HttpRuleParser.cs" />
     <Compile Include="System\Net\Http\HttpTelemetry.cs" />

src/libraries/System.Net.Http/src/System/Net/Http/BrowserHttpHandler/BrowserHttpHandler.cs

@@ -129,7 +129,7 @@ protected internal override async Task<HttpResponseMessage> SendAsync(HttpReques
             {
                 var requestObject = new JSObject();
 
-                if (request.Properties.TryGetValue("WebAssemblyFetchOptions", out object? fetchOptionsValue) &&
+                if (request.Options.TryGetValue("WebAssemblyFetchOptions", out object? fetchOptionsValue) &&
                     fetchOptionsValue is IDictionary<string, object> fetchOptions)
                 {
                     foreach (KeyValuePair<string, object> item in fetchOptions)
@@ -221,7 +221,7 @@ protected internal override async Task<HttpResponseMessage> SendAsync(HttpReques
 
                 HttpResponseMessage httpResponse = new HttpResponseMessage((HttpStatusCode)status.Status);
 
-                bool streamingEnabled = request.Properties.TryGetValue("WebAssemblyEnableStreamingResponse", out object? streamingEnabledValue) && (bool)(streamingEnabledValue ?? false);
+                bool streamingEnabled = request.Options.TryGetValue("WebAssemblyEnableStreamingResponse", out object? streamingEnabledValue) && (bool)(streamingEnabledValue ?? false);
 
                 httpResponse.Content = StreamingSupported && streamingEnabled
                     ? new StreamContent(wasmHttpReadStream = new WasmHttpReadStream(status))

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestMessage.cs

@@ -24,7 +24,7 @@ public class HttpRequestMessage : IDisposable
         private Version _version;
         private HttpContent? _content;
         private bool _disposed;
-        private IDictionary<string, object?>? _properties;
+        private HttpRequestOptions? _options;
 
         public Version Version
         {
@@ -111,17 +111,10 @@ public HttpRequestHeaders Headers
 
         internal bool HasHeaders => _headers != null;
 
-        public IDictionary<string, object?> Properties
-        {
-            get
-            {
-                if (_properties == null)
-                {
-                    _properties = new Dictionary<string, object?>();
-                }
-                return _properties;
-            }
-        }
+        [Obsolete("Use Options instead.")]
+        public IDictionary<string, object?> Properties => Options;
+
+        public HttpRequestOptions Options => _options ??= new HttpRequestOptions();
 
         public HttpRequestMessage()
             : this(HttpMethod.Get, (Uri?)null)

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptions.cs

@@ -0,0 +1,10 @@
+// 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.Collections.Generic;
+
+namespace System.Net.Http
+{
+    public sealed class HttpRequestOptions : Dictionary<string, object?> { }
+}

src/libraries/System.Net.Http/src/System/Net/Http/HttpRequestOptionsKey.cs

@@ -0,0 +1,17 @@
+// 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.Net.Http
+{
+    public readonly struct HttpRequestOptionsKey<TValue>
+    {
+        private readonly string _key;
+        public HttpRequestOptionsKey(string key)
+        {
+            _key = key;
+        }
+        public string Key => _key;
+    }
+}