[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<TKey>
+    {
+        public HttpRequestOptionsKey(TKey key) {}
+        public TKey Key { get { throw null; } }
+    }
+
+    public sealed class HttpRequestOptions : System.Collections.Generic.Dictionary<HttpRequestOptionsKey<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(new HttpRequestOptionsKey<string>("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(new HttpRequestOptionsKey<string>("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

@@ -25,6 +25,7 @@ public class HttpRequestMessage : IDisposable
         private HttpContent? _content;
         private bool _disposed;
         private IDictionary<string, object?>? _properties;
+        private HttpRequestOptions? _options;
 
         public Version Version
         {
@@ -111,6 +112,7 @@ public HttpRequestHeaders Headers
 
         internal bool HasHeaders => _headers != null;
 
+        [Obsolete("Use Options instead.")]
         public IDictionary<string, object?> Properties
         {
             get
@@ -123,6 +125,18 @@ public HttpRequestHeaders Headers
             }
         }
 
+        public HttpRequestOptions Options
+        {
+            get
+            {
+                if (_options == null)
+                {
+                    _options = new HttpRequestOptions();
+                }
+                return _options;
+            }
+        }
+
         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<HttpRequestOptionsKey<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<TKey>
+    {
+        private readonly TKey _key;
+        public HttpRequestOptionsKey(TKey key)
+        {
+            _key = key;
+        }
+        public TKey Key => _key;
+    }
+}