Add documentation to System.Net

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

@@ -9,7 +9,8 @@ namespace System.Net.Http
     /// Represents a method that specifies the <see cref="Encoding"/> to use when interpreting header values.
     /// </summary>
     /// <param name="headerName">Name of the header to specify the <see cref="Encoding"/> for.</param>
-    /// <param name="context">The <typeparamref name="TContext"/> we are enoding/decoding the headers for.</param>
+    /// <param name="context">The <typeparamref name="TContext"/> we are encoding/decoding the headers for.</param>
+    /// <typeparam name="TContext">The type which headers are being encoded/decoded;</typeparam>
     /// <returns><see cref="Encoding"/> to use or <see langword="null"/> to use the default behavior.</returns>
     public delegate Encoding? HeaderEncodingSelector<TContext>(string headerName, TContext context);
 }

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

@@ -551,6 +551,17 @@ private async Task LoadIntoBufferAsyncCore(Task serializeToStreamTask, MemoryStr
             }
         }
 
+        /// <summary>
+        /// Serializes the HTTP content to a memory stream.
+        /// </summary>
+        /// <param name="cancellationToken">The cancellation token to cancel the operation.</param>
+        /// <returns>The output memory stream which contains the serialized HTTP content.</returns>
+        /// <remarks>
+        /// Once the operation completes, the returned memory stream represents the HTTP content. The returned stream can then be used to read the content using various stream APIs.
+        /// The <see cref="CreateContentReadStream(CancellationToken)"/> method buffers the content to a memory stream.
+        /// Derived classes can override this behavior if there is a better way to retrieve the content as stream.
+        /// For example, a byte array or a string could use a more efficient method way such as wrapping a read-only MemoryStream around the bytes or string.
+        /// </remarks>
         protected virtual Stream CreateContentReadStream(CancellationToken cancellationToken)
         {
             LoadIntoBuffer(MaxBufferSize, cancellationToken);

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

@@ -418,6 +418,9 @@ public Func<SocketsHttpPlaintextStreamFilterContext, CancellationToken, ValueTas
             }
         }
 
+        /// <summary>
+        /// Gets a writable dictionary (that is, a map) of custom properties for the HttpClient requests. The dictionary is initialized empty; you can insert and query key-value pairs for your custom handlers and special processing.
+        /// </summary>
         public IDictionary<string, object?> Properties =>
             _settings._properties ?? (_settings._properties = new Dictionary<string, object?>());
 

src/libraries/System.Net.Security/src/System/Net/Security/NegotiateStream.cs

@@ -460,6 +460,7 @@ public override void Write(byte[] buffer, int offset, int count)
             WriteAsync(new SyncReadWriteAdapter(InnerStream), new ReadOnlyMemory<byte>(buffer, offset, count)).GetAwaiter().GetResult();
         }
 
+        /// <returns>A <see cref="Task"/> that represents the asynchronous read operation.</returns>
         public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
         {
             ValidateBufferArguments(buffer, offset, count);
@@ -473,6 +474,7 @@ public override Task WriteAsync(byte[] buffer, int offset, int count, Cancellati
             return WriteAsync(new AsyncReadWriteAdapter(InnerStream, cancellationToken), new ReadOnlyMemory<byte>(buffer, offset, count));
         }
 
+        /// <returns>A <see cref="ValueTask"/> that represents the asynchronous read operation.</returns>
         public override ValueTask WriteAsync(ReadOnlyMemory<byte> buffer, CancellationToken cancellationToken = default)
         {
             ThrowIfFailed(authSuccessCheck: true);