dotnet-core/release-notes/2.1/Preview/api-diff/preview1/2.1-preview1_System.Net.Http.md

System.Net.Http

 namespace System.Net.Http {
     public class HttpClient : HttpMessageInvoker {
+        public Task<HttpResponseMessage> PatchAsync(string requestUri, HttpContent content);
+        public Task<HttpResponseMessage> PatchAsync(string requestUri, HttpContent content, CancellationToken cancellationToken);
+        public Task<HttpResponseMessage> PatchAsync(Uri requestUri, HttpContent content);
+        public Task<HttpResponseMessage> PatchAsync(Uri requestUri, HttpContent content, CancellationToken cancellationToken);
     }
     public class HttpMethod : IEquatable<HttpMethod> {
+        public static HttpMethod Patch { get; }
     }
+    public sealed class ReadOnlyMemoryContent : HttpContent {
+        public ReadOnlyMemoryContent(ReadOnlyMemory<byte> content);
+        protected override Task SerializeToStreamAsync(Stream stream, TransportContext context);
+        protected internal override bool TryComputeLength(out long length);
+    }
 }