Merge pull request #1504 from jtattermusch/csharp_api_fixes

Polishing the new C# API

32 files changed, 206 insertions, 62 deletions

diff --git a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
index caa6220f2c..b69b933aba 100644
--- a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
@@ -84,7 +84,7 @@ namespace Grpc.Core.Tests
         {
             server = new Server();
             server.AddServiceDefinition(ServiceDefinition);
-            int port = server.AddListeningPort(Host + ":0");
+            int port = server.AddListeningPort(Host, Server.PickUnusedPort);
             server.Start();
             channel = new Channel(Host + ":" + port);
         }
@@ -220,7 +220,7 @@ namespace Grpc.Core.Tests
             }
         }
 
-        private static async Task<string> EchoHandler(string request)
+        private static async Task<string> EchoHandler(ServerCallContext context, string request)
         {
             if (request == "THROW")
             {
@@ -229,7 +229,7 @@ namespace Grpc.Core.Tests
             return request;
         }
 
-        private static async Task<string> ConcatAndEchoHandler(IAsyncStreamReader<string> requestStream)
+        private static async Task<string> ConcatAndEchoHandler(ServerCallContext context, IAsyncStreamReader<string> requestStream)
         {
             string result = "";
             await requestStream.ForEach(async (request) =>
diff --git a/src/csharp/Grpc.Core.Tests/ServerTest.cs b/src/csharp/Grpc.Core.Tests/ServerTest.cs
index 2a1855da67..02c773c9cc 100644
--- a/src/csharp/Grpc.Core.Tests/ServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ServerTest.cs
@@ -47,7 +47,7 @@ namespace Grpc.Core.Tests
             GrpcEnvironment.Initialize();
 
             Server server = new Server();
-            server.AddListeningPort("localhost:0");
+            server.AddListeningPort("localhost", Server.PickUnusedPort);
             server.Start();
             server.ShutdownAsync().Wait();
 
diff --git a/src/csharp/Grpc.Core/AsyncClientStreamingCall.cs b/src/csharp/Grpc.Core/AsyncClientStreamingCall.cs
index e81ce01ebb..b95776f66d 100644
--- a/src/csharp/Grpc.Core/AsyncClientStreamingCall.cs
+++ b/src/csharp/Grpc.Core/AsyncClientStreamingCall.cs
@@ -40,7 +40,9 @@ namespace Grpc.Core
     /// <summary>
     /// Return type for client streaming calls.
     /// </summary>
-    public struct AsyncClientStreamingCall<TRequest, TResponse>
+    public sealed class AsyncClientStreamingCall<TRequest, TResponse>
+        where TRequest : class
+        where TResponse : class
     {
         readonly IClientStreamWriter<TRequest> requestStream;
         readonly Task<TResponse> result;
diff --git a/src/csharp/Grpc.Core/AsyncDuplexStreamingCall.cs b/src/csharp/Grpc.Core/AsyncDuplexStreamingCall.cs
index 1cb30f4779..ee05437416 100644
--- a/src/csharp/Grpc.Core/AsyncDuplexStreamingCall.cs
+++ b/src/csharp/Grpc.Core/AsyncDuplexStreamingCall.cs
@@ -40,7 +40,9 @@ namespace Grpc.Core
     /// <summary>
     /// Return type for bidirectional streaming calls.
     /// </summary>
-    public struct AsyncDuplexStreamingCall<TRequest, TResponse>
+    public sealed class AsyncDuplexStreamingCall<TRequest, TResponse>
+        where TRequest : class
+        where TResponse : class
     {
         readonly IClientStreamWriter<TRequest> requestStream;
         readonly IAsyncStreamReader<TResponse> responseStream;
diff --git a/src/csharp/Grpc.Core/AsyncServerStreamingCall.cs b/src/csharp/Grpc.Core/AsyncServerStreamingCall.cs
index d614916fb7..73b9614985 100644
--- a/src/csharp/Grpc.Core/AsyncServerStreamingCall.cs
+++ b/src/csharp/Grpc.Core/AsyncServerStreamingCall.cs
@@ -40,7 +40,8 @@ namespace Grpc.Core
     /// <summary>
     /// Return type for server streaming calls.
     /// </summary>
-    public struct AsyncServerStreamingCall<TResponse>
+    public sealed class AsyncServerStreamingCall<TResponse>
+        where TResponse : class
     {
         readonly IAsyncStreamReader<TResponse> responseStream;
 
diff --git a/src/csharp/Grpc.Core/Call.cs b/src/csharp/Grpc.Core/Call.cs
index 070dfb569d..771cc083da 100644
--- a/src/csharp/Grpc.Core/Call.cs
+++ b/src/csharp/Grpc.Core/Call.cs
@@ -41,6 +41,8 @@ namespace Grpc.Core
     /// Abstraction of a call to be invoked on a client.
     /// </summary>
     public class Call<TRequest, TResponse>
+        where TRequest : class
+        where TResponse : class
     {
         readonly string name;
         readonly Marshaller<TRequest> requestMarshaller;
diff --git a/src/csharp/Grpc.Core/Calls.cs b/src/csharp/Grpc.Core/Calls.cs
index a8d2b9498e..ba42a2d4f8 100644
--- a/src/csharp/Grpc.Core/Calls.cs
+++ b/src/csharp/Grpc.Core/Calls.cs
@@ -44,6 +44,8 @@ namespace Grpc.Core
     public static class Calls
     {
         public static TResponse BlockingUnaryCall<TRequest, TResponse>(Call<TRequest, TResponse> call, TRequest req, CancellationToken token)
+            where TRequest : class
+            where TResponse : class
         {
             var asyncCall = new AsyncCall<TRequest, TResponse>(call.RequestMarshaller.Serializer, call.ResponseMarshaller.Deserializer);
             // TODO(jtattermusch): this gives a race that cancellation can be requested before the call even starts.
@@ -52,6 +54,8 @@ namespace Grpc.Core
         }
 
         public static async Task<TResponse> AsyncUnaryCall<TRequest, TResponse>(Call<TRequest, TResponse> call, TRequest req, CancellationToken token)
+            where TRequest : class
+            where TResponse : class
         {
             var asyncCall = new AsyncCall<TRequest, TResponse>(call.RequestMarshaller.Serializer, call.ResponseMarshaller.Deserializer);
             asyncCall.Initialize(call.Channel, GetCompletionQueue(), call.Name);
@@ -61,6 +65,8 @@ namespace Grpc.Core
         }
 
         public static AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(Call<TRequest, TResponse> call, TRequest req, CancellationToken token)
+            where TRequest : class
+            where TResponse : class
         {
             var asyncCall = new AsyncCall<TRequest, TResponse>(call.RequestMarshaller.Serializer, call.ResponseMarshaller.Deserializer);
             asyncCall.Initialize(call.Channel, GetCompletionQueue(), call.Name);
@@ -71,6 +77,8 @@ namespace Grpc.Core
         }
 
         public static AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(Call<TRequest, TResponse> call, CancellationToken token)
+            where TRequest : class
+            where TResponse : class
         {
             var asyncCall = new AsyncCall<TRequest, TResponse>(call.RequestMarshaller.Serializer, call.ResponseMarshaller.Deserializer);
             asyncCall.Initialize(call.Channel, GetCompletionQueue(), call.Name);
@@ -81,6 +89,8 @@ namespace Grpc.Core
         }
 
         public static AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(Call<TRequest, TResponse> call, CancellationToken token)
+            where TRequest : class
+            where TResponse : class
         {
             var asyncCall = new AsyncCall<TRequest, TResponse>(call.RequestMarshaller.Serializer, call.ResponseMarshaller.Deserializer);
             asyncCall.Initialize(call.Channel, GetCompletionQueue(), call.Name);
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 9c91541d90..f5f2cf5f22 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -96,6 +96,7 @@
     <Compile Include="Internal\ServerResponseStream.cs" />
     <Compile Include="Internal\AtomicCounter.cs" />
     <Compile Include="Internal\DebugStats.cs" />
+    <Compile Include="ServerCallContext.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />
diff --git a/src/csharp/Grpc.Core/IAsyncStreamReader.cs b/src/csharp/Grpc.Core/IAsyncStreamReader.cs
index 61cf57f7e0..699741cd05 100644
--- a/src/csharp/Grpc.Core/IAsyncStreamReader.cs
+++ b/src/csharp/Grpc.Core/IAsyncStreamReader.cs
@@ -44,9 +44,10 @@ namespace Grpc.Core
     /// </summary>
     /// <typeparam name="T"></typeparam>
     public interface IAsyncStreamReader<T>
+        where T : class
     {
         /// <summary>
-        /// Reads a single message. Returns default(T) if the last message was already read.
+        /// Reads a single message. Returns null if the last message was already read.
         /// A following read can only be started when the previous one finishes.
         /// </summary>
         Task<T> ReadNext();
diff --git a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
index 724bae8f31..4bd8bfb8df 100644
--- a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
+++ b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
@@ -44,6 +44,7 @@ namespace Grpc.Core
     /// </summary>
     /// <typeparam name="T"></typeparam>
     public interface IAsyncStreamWriter<T>
+        where T : class
     {
         /// <summary>
         /// Writes a single message. Only one write can be pending at a time.
diff --git a/src/csharp/Grpc.Core/IClientStreamWriter.cs b/src/csharp/Grpc.Core/IClientStreamWriter.cs
index 6da42e9ccc..0847a928e6 100644
--- a/src/csharp/Grpc.Core/IClientStreamWriter.cs
+++ b/src/csharp/Grpc.Core/IClientStreamWriter.cs
@@ -44,6 +44,7 @@ namespace Grpc.Core
     /// </summary>
     /// <typeparam name="T"></typeparam>
     public interface IClientStreamWriter<T> : IAsyncStreamWriter<T>
+        where T : class
     {
         /// <summary>
         /// Closes the stream. Can only be called once there is no pending write. No writes should follow calling this.
diff --git a/src/csharp/Grpc.Core/IServerStreamWriter.cs b/src/csharp/Grpc.Core/IServerStreamWriter.cs
index e76397d8a0..199a585a3f 100644
--- a/src/csharp/Grpc.Core/IServerStreamWriter.cs
+++ b/src/csharp/Grpc.Core/IServerStreamWriter.cs
@@ -43,6 +43,7 @@ namespace Grpc.Core
     /// A writable stream of messages that is used in server-side handlers.
     /// </summary>
     public interface IServerStreamWriter<T> : IAsyncStreamWriter<T>
+        where T : class
     {
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index 3c66c67dcc..171d0c799d 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -138,9 +138,7 @@ namespace Grpc.Core.Internal
 
                 ReleaseResourcesIfPossible();
             }
-            // TODO(jtattermusch): check if call was cancelled.
-
-            // TODO: handle error ...
+            // TODO(jtattermusch): handle error
 
             finishedServersideTcs.SetResult(null);
         }
diff --git a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
index 6854922a6f..1697058732 100644
--- a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
@@ -38,6 +38,8 @@ namespace Grpc.Core.Internal
     /// Writes requests asynchronously to an underlying AsyncCall object.
     /// </summary>
     internal class ClientRequestStream<TRequest, TResponse> : IClientStreamWriter<TRequest>
+        where TRequest : class
+        where TResponse : class
     {
         readonly AsyncCall<TRequest, TResponse> call;
 
diff --git a/src/csharp/Grpc.Core/Internal/ClientResponseStream.cs b/src/csharp/Grpc.Core/Internal/ClientResponseStream.cs
index 7fa511faa8..b2378cade6 100644
--- a/src/csharp/Grpc.Core/Internal/ClientResponseStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ClientResponseStream.cs
@@ -38,6 +38,8 @@ using System.Threading.Tasks;
 namespace Grpc.Core.Internal
 {
     internal class ClientResponseStream<TRequest, TResponse> : IAsyncStreamReader<TResponse>
+        where TRequest : class
+        where TResponse : class
     {
         readonly AsyncCall<TRequest, TResponse> call;
 
diff --git a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
index 01b2a11369..95d8e97869 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
@@ -45,6 +45,8 @@ namespace Grpc.Core.Internal
     }
 
     internal class UnaryServerCallHandler<TRequest, TResponse> : IServerCallHandler
+        where TRequest : class
+        where TResponse : class
     {
         readonly Method<TRequest, TResponse> method;
         readonly UnaryServerMethod<TRequest, TResponse> handler;
@@ -72,7 +74,8 @@ namespace Grpc.Core.Internal
                 var request = await requestStream.ReadNext();
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                 Preconditions.CheckArgument(await requestStream.ReadNext() == null);
-                var result = await handler(request);
+                var context = new ServerCallContext();  // TODO(jtattermusch): initialize the context
+                var result = await handler(context, request);
                 await responseStream.Write(result);
             } 
             catch (Exception e)
@@ -93,6 +96,8 @@ namespace Grpc.Core.Internal
     }
 
     internal class ServerStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
+        where TRequest : class
+        where TResponse : class
     {
         readonly Method<TRequest, TResponse> method;
         readonly ServerStreamingServerMethod<TRequest, TResponse> handler;
@@ -121,7 +126,8 @@ namespace Grpc.Core.Internal
                 // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                 Preconditions.CheckArgument(await requestStream.ReadNext() == null);
 
-                await handler(request, responseStream);
+                var context = new ServerCallContext();  // TODO(jtattermusch): initialize the context
+                await handler(context, request, responseStream);
             }
             catch (Exception e)
             {
@@ -142,6 +148,8 @@ namespace Grpc.Core.Internal
     }
 
     internal class ClientStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
+        where TRequest : class
+        where TResponse : class
     {
         readonly Method<TRequest, TResponse> method;
         readonly ClientStreamingServerMethod<TRequest, TResponse> handler;
@@ -162,11 +170,12 @@ namespace Grpc.Core.Internal
             var finishedTask = asyncCall.ServerSideCallAsync();
             var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
+            var context = new ServerCallContext();  // TODO(jtattermusch): initialize the context
 
             Status status = Status.DefaultSuccess;
             try
             {
-                var result = await handler(requestStream);
+                var result = await handler(context, requestStream);
                 try
                 {
                     await responseStream.Write(result);
@@ -195,6 +204,8 @@ namespace Grpc.Core.Internal
     }
 
     internal class DuplexStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
+        where TRequest : class
+        where TResponse : class
     {
         readonly Method<TRequest, TResponse> method;
         readonly DuplexStreamingServerMethod<TRequest, TResponse> handler;
@@ -215,11 +226,12 @@ namespace Grpc.Core.Internal
             var finishedTask = asyncCall.ServerSideCallAsync();
             var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
+            var context = new ServerCallContext();  // TODO(jtattermusch): initialize the context
 
             Status status = Status.DefaultSuccess;
             try
             {
-                await handler(requestStream, responseStream);
+                await handler(context, requestStream, responseStream);
             }
             catch (Exception e)
             {
diff --git a/src/csharp/Grpc.Core/Internal/ServerCalls.cs b/src/csharp/Grpc.Core/Internal/ServerCalls.cs
index 5c6b335c7f..81279678b9 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCalls.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCalls.cs
@@ -41,21 +41,29 @@ namespace Grpc.Core.Internal
     internal static class ServerCalls
     {
         public static IServerCallHandler UnaryCall<TRequest, TResponse>(Method<TRequest, TResponse> method, UnaryServerMethod<TRequest, TResponse> handler)
+            where TRequest : class
+            where TResponse : class
         {
             return new UnaryServerCallHandler<TRequest, TResponse>(method, handler);
         }
 
         public static IServerCallHandler ClientStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, ClientStreamingServerMethod<TRequest, TResponse> handler)
+            where TRequest : class
+            where TResponse : class
         {
             return new ClientStreamingServerCallHandler<TRequest, TResponse>(method, handler);
         }
 
         public static IServerCallHandler ServerStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, ServerStreamingServerMethod<TRequest, TResponse> handler)
+            where TRequest : class
+            where TResponse : class
         {
             return new ServerStreamingServerCallHandler<TRequest, TResponse>(method, handler);
         }
 
         public static IServerCallHandler DuplexStreamingCall<TRequest, TResponse>(Method<TRequest, TResponse> method, DuplexStreamingServerMethod<TRequest, TResponse> handler)
+            where TRequest : class
+            where TResponse : class
         {
             return new DuplexStreamingServerCallHandler<TRequest, TResponse>(method, handler);
         }
diff --git a/src/csharp/Grpc.Core/Internal/ServerRequestStream.cs b/src/csharp/Grpc.Core/Internal/ServerRequestStream.cs
index aa311059c3..d9ee0c815b 100644
--- a/src/csharp/Grpc.Core/Internal/ServerRequestStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerRequestStream.cs
@@ -38,6 +38,8 @@ using System.Threading.Tasks;
 namespace Grpc.Core.Internal
 {
     internal class ServerRequestStream<TRequest, TResponse> : IAsyncStreamReader<TRequest>
+        where TRequest : class
+        where TResponse : class
     {
         readonly AsyncCallServer<TRequest, TResponse> call;
 
diff --git a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
index 686017c048..da688d504f 100644
--- a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
@@ -39,6 +39,8 @@ namespace Grpc.Core.Internal
     /// Writes responses asynchronously to an underlying AsyncCallServer object.
     /// </summary>
     internal class ServerResponseStream<TRequest, TResponse> : IServerStreamWriter<TResponse>
+        where TRequest : class
+        where TResponse : class
     {
         readonly AsyncCallServer<TRequest, TResponse> call;
 
diff --git a/src/csharp/Grpc.Core/Server.cs b/src/csharp/Grpc.Core/Server.cs
index a3000cee46..0df46bb25b 100644
--- a/src/csharp/Grpc.Core/Server.cs
+++ b/src/csharp/Grpc.Core/Server.cs
@@ -47,6 +47,11 @@ namespace Grpc.Core
     /// </summary>
     public class Server
     {
+        /// <summary>
+        /// Pass this value as port to have the server choose an unused listening port for you.
+        /// </summary>
+        public const int PickUnusedPort = 0;
+
         // TODO(jtattermusch) : make sure the delegate doesn't get garbage collected while
         // native callbacks are in the completion queue.
         readonly ServerShutdownCallbackDelegate serverShutdownHandler;
@@ -89,29 +94,25 @@ namespace Grpc.Core
         /// Add a non-secure port on which server should listen.
         /// Only call this before Start().
         /// </summary>
-        public int AddListeningPort(string addr)
+        /// <returns>The port on which server will be listening.</returns>
+        /// <param name="host">the host</param>
+        /// <param name="port">the port. If zero, an unused port is chosen automatically.</param>
+        public int AddListeningPort(string host, int port)
         {
-            lock (myLock)
-            {
-                Preconditions.CheckState(!startRequested);
-                return handle.AddListeningPort(addr);
-            }
+            return AddListeningPortInternal(host, port, null);
         }
 
         /// <summary>
-        /// Add a secure port on which server should listen.
+        /// Add a non-secure port on which server should listen.
         /// Only call this before Start().
         /// </summary>
-        public int AddListeningPort(string addr, ServerCredentials credentials)
+        /// <returns>The port on which server will be listening.</returns>
+        /// <param name="host">the host</param>
+        /// <param name="port">the port. If zero, , an unused port is chosen automatically.</param>
+        public int AddListeningPort(string host, int port, ServerCredentials credentials)
         {
-            lock (myLock)
-            {
-                Preconditions.CheckState(!startRequested);
-                using (var nativeCredentials = credentials.ToNativeCredentials())
-                {
-                    return handle.AddListeningPort(addr, nativeCredentials);
-                }
-            }
+            Preconditions.CheckNotNull(credentials);
+            return AddListeningPortInternal(host, port, credentials);
         }
 
         /// <summary>
@@ -164,6 +165,26 @@ namespace Grpc.Core
             handle.Dispose();
         }
 
+        private int AddListeningPortInternal(string host, int port, ServerCredentials credentials)
+        {
+            lock (myLock)
+            {
+                Preconditions.CheckState(!startRequested);    
+                var address = string.Format("{0}:{1}", host, port);
+                if (credentials != null)
+                {
+                    using (var nativeCredentials = credentials.ToNativeCredentials())
+                    {
+                        return handle.AddListeningPort(address, nativeCredentials);
+                    }
+                }
+                else
+                {
+                    return handle.AddListeningPort(address);    
+                }
+            }
+        }
+
         /// <summary>
         /// Allows one new RPC call to be received by server.
         /// </summary>
diff --git a/src/csharp/Grpc.Core/ServerCallContext.cs b/src/csharp/Grpc.Core/ServerCallContext.cs
new file mode 100644
index 0000000000..e873b3e88a
--- /dev/null
+++ b/src/csharp/Grpc.Core/ServerCallContext.cs
@@ -0,0 +1,56 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Context for a server-side call.
+    /// </summary>
+    public sealed class ServerCallContext
+    {
+        
+        // TODO(jtattermusch): add cancellationToken
+
+        // TODO(jtattermusch): add deadline info
+
+        // TODO(jtattermusch): expose initial metadata sent by client for reading
+
+        // TODO(jtattermusch): expose method to send initial metadata back to client
+
+        // TODO(jtattermusch): allow setting status and trailing metadata to send after handler completes.
+    }
+}
diff --git a/src/csharp/Grpc.Core/ServerMethods.cs b/src/csharp/Grpc.Core/ServerMethods.cs
index 6646bb5a89..377b78eb30 100644
--- a/src/csharp/Grpc.Core/ServerMethods.cs
+++ b/src/csharp/Grpc.Core/ServerMethods.cs
@@ -42,20 +42,28 @@ namespace Grpc.Core
     /// <summary>
     /// Server-side handler for unary call.
     /// </summary>
-    public delegate Task<TResponse> UnaryServerMethod<TRequest, TResponse>(TRequest request);
+    public delegate Task<TResponse> UnaryServerMethod<TRequest, TResponse>(ServerCallContext context, TRequest request)
+        where TRequest : class
+        where TResponse : class;
 
     /// <summary>
     /// Server-side handler for client streaming call.
     /// </summary>
-    public delegate Task<TResponse> ClientStreamingServerMethod<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream);
+    public delegate Task<TResponse> ClientStreamingServerMethod<TRequest, TResponse>(ServerCallContext context, IAsyncStreamReader<TRequest> requestStream)
+        where TRequest : class
+        where TResponse : class;
 
     /// <summary>
     /// Server-side handler for server streaming call.
     /// </summary>
-    public delegate Task ServerStreamingServerMethod<TRequest, TResponse>(TRequest request, IServerStreamWriter<TResponse> responseStream);
+    public delegate Task ServerStreamingServerMethod<TRequest, TResponse>(ServerCallContext context, TRequest request, IServerStreamWriter<TResponse> responseStream)
+        where TRequest : class
+        where TResponse : class;
 
     /// <summary>
     /// Server-side handler for bidi streaming call.
     /// </summary>
-    public delegate Task DuplexStreamingServerMethod<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, IServerStreamWriter<TResponse> responseStream);
+    public delegate Task DuplexStreamingServerMethod<TRequest, TResponse>(ServerCallContext context, IAsyncStreamReader<TRequest> requestStream, IServerStreamWriter<TResponse> responseStream)
+        where TRequest : class
+        where TResponse : class;
 }
diff --git a/src/csharp/Grpc.Core/ServerServiceDefinition.cs b/src/csharp/Grpc.Core/ServerServiceDefinition.cs
index 01b1dc8f7b..81846beb2f 100644
--- a/src/csharp/Grpc.Core/ServerServiceDefinition.cs
+++ b/src/csharp/Grpc.Core/ServerServiceDefinition.cs
@@ -76,6 +76,8 @@ namespace Grpc.Core
             public Builder AddMethod<TRequest, TResponse>(
                 Method<TRequest, TResponse> method,
                 UnaryServerMethod<TRequest, TResponse> handler)
+                    where TRequest : class
+                    where TResponse : class
             {
                 callHandlers.Add(GetFullMethodName(serviceName, method.Name), ServerCalls.UnaryCall(method, handler));
                 return this;
@@ -84,6 +86,8 @@ namespace Grpc.Core
             public Builder AddMethod<TRequest, TResponse>(
                 Method<TRequest, TResponse> method,
                 ClientStreamingServerMethod<TRequest, TResponse> handler)
+                    where TRequest : class
+                    where TResponse : class
             {
                 callHandlers.Add(GetFullMethodName(serviceName, method.Name), ServerCalls.ClientStreamingCall(method, handler));
                 return this;
@@ -92,6 +96,8 @@ namespace Grpc.Core
             public Builder AddMethod<TRequest, TResponse>(
                 Method<TRequest, TResponse> method,
                 ServerStreamingServerMethod<TRequest, TResponse> handler)
+                    where TRequest : class
+                    where TResponse : class
             {
                 callHandlers.Add(GetFullMethodName(serviceName, method.Name), ServerCalls.ServerStreamingCall(method, handler));
                 return this;
@@ -100,6 +106,8 @@ namespace Grpc.Core
             public Builder AddMethod<TRequest, TResponse>(
                 Method<TRequest, TResponse> method,
                 DuplexStreamingServerMethod<TRequest, TResponse> handler)
+                    where TRequest : class
+                    where TResponse : class
             {
                 callHandlers.Add(GetFullMethodName(serviceName, method.Name), ServerCalls.DuplexStreamingCall(method, handler));
                 return this;
diff --git a/src/csharp/Grpc.Core/Stub/AbstractStub.cs b/src/csharp/Grpc.Core/Stub/AbstractStub.cs
index cf5ab958c5..4a8b254357 100644
--- a/src/csharp/Grpc.Core/Stub/AbstractStub.cs
+++ b/src/csharp/Grpc.Core/Stub/AbstractStub.cs
@@ -64,6 +64,8 @@ namespace Grpc.Core
         /// Creates a new call to given method.
         /// </summary>
         protected Call<TRequest, TResponse> CreateCall<TRequest, TResponse>(string serviceName, Method<TRequest, TResponse> method)
+            where TRequest : class
+            where TResponse : class
         {
             var headerBuilder = Metadata.CreateBuilder();
             config.HeaderInterceptor(headerBuilder);
diff --git a/src/csharp/Grpc.Examples.MathServer/MathServer.cs b/src/csharp/Grpc.Examples.MathServer/MathServer.cs
index abc7ef05e4..cfde9b42c7 100644
--- a/src/csharp/Grpc.Examples.MathServer/MathServer.cs
+++ b/src/csharp/Grpc.Examples.MathServer/MathServer.cs
@@ -46,7 +46,7 @@ namespace math
 
             Server server = new Server();
             server.AddServiceDefinition(MathGrpc.BindService(new MathServiceImpl()));
-            int port = server.AddListeningPort(host + ":23456");
+            int port = server.AddListeningPort(host, 23456);
             server.Start();
 
             Console.WriteLine("MathServer listening on port " + port);
diff --git a/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs b/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
index 332795e0e5..4ada95edd6 100644
--- a/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
+++ b/src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs
@@ -59,7 +59,7 @@ namespace math.Tests
 
             server = new Server();
             server.AddServiceDefinition(MathGrpc.BindService(new MathServiceImpl()));
-            int port = server.AddListeningPort(host + ":0");
+            int port = server.AddListeningPort(host, Server.PickUnusedPort);
             server.Start();
             channel = new Channel(host + ":" + port);
 
diff --git a/src/csharp/Grpc.Examples/MathGrpc.cs b/src/csharp/Grpc.Examples/MathGrpc.cs
index 60408b9018..03f5c31cb7 100644
--- a/src/csharp/Grpc.Examples/MathGrpc.cs
+++ b/src/csharp/Grpc.Examples/MathGrpc.cs
@@ -133,13 +133,13 @@ namespace math
         // server-side interface
         public interface IMathService
         {
-            Task<DivReply> Div(DivArgs request);
+            Task<DivReply> Div(ServerCallContext context, DivArgs request);
 
-            Task Fib(FibArgs request, IServerStreamWriter<Num> responseStream);
+            Task Fib(ServerCallContext context, FibArgs request, IServerStreamWriter<Num> responseStream);
 
-            Task<Num> Sum(IAsyncStreamReader<Num> requestStream);
+            Task<Num> Sum(ServerCallContext context, IAsyncStreamReader<Num> requestStream);
 
-            Task DivMany(IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream);
+            Task DivMany(ServerCallContext context, IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream);
         }
 
         public static ServerServiceDefinition BindService(IMathService serviceImpl)
diff --git a/src/csharp/Grpc.Examples/MathServiceImpl.cs b/src/csharp/Grpc.Examples/MathServiceImpl.cs
index 83ec2a8c3d..800dee8735 100644
--- a/src/csharp/Grpc.Examples/MathServiceImpl.cs
+++ b/src/csharp/Grpc.Examples/MathServiceImpl.cs
@@ -46,12 +46,12 @@ namespace math
     /// </summary>
     public class MathServiceImpl : MathGrpc.IMathService
     {
-        public Task<DivReply> Div(DivArgs request)
+        public Task<DivReply> Div(ServerCallContext context, DivArgs request)
         {
             return Task.FromResult(DivInternal(request));
         }
 
-        public async Task Fib(FibArgs request, IServerStreamWriter<Num> responseStream)
+        public async Task Fib(ServerCallContext context, FibArgs request, IServerStreamWriter<Num> responseStream)
         {
             if (request.Limit <= 0)
             {
@@ -68,7 +68,7 @@ namespace math
             }
         }
 
-        public async Task<Num> Sum(IAsyncStreamReader<Num> requestStream)
+        public async Task<Num> Sum(ServerCallContext context, IAsyncStreamReader<Num> requestStream)
         {
             long sum = 0;
             await requestStream.ForEach(async num =>
@@ -78,7 +78,7 @@ namespace math
             return Num.CreateBuilder().SetNum_(sum).Build();
         }
 
-        public async Task DivMany(IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream)
+        public async Task DivMany(ServerCallContext context, IAsyncStreamReader<DivArgs> requestStream, IServerStreamWriter<DivReply> responseStream)
         {
             await requestStream.ForEach(async divArgs =>
             {
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs b/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
index 45380227c2..9e49ce0d17 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropClientServerTest.cs
@@ -59,7 +59,7 @@ namespace Grpc.IntegrationTesting
 
             server = new Server();
             server.AddServiceDefinition(TestServiceGrpc.BindService(new TestServiceImpl()));
-            int port = server.AddListeningPort(host + ":0", TestCredentials.CreateTestServerCredentials());
+            int port = server.AddListeningPort(host, Server.PickUnusedPort, TestCredentials.CreateTestServerCredentials());
             server.Start();
 
             var channelArgs = ChannelArgs.CreateBuilder()
diff --git a/src/csharp/Grpc.IntegrationTesting/InteropServer.cs b/src/csharp/Grpc.IntegrationTesting/InteropServer.cs
index ad5200774f..ca54aed041 100644
--- a/src/csharp/Grpc.IntegrationTesting/InteropServer.cs
+++ b/src/csharp/Grpc.IntegrationTesting/InteropServer.cs
@@ -93,16 +93,17 @@ namespace Grpc.IntegrationTesting
             var server = new Server();
             server.AddServiceDefinition(TestServiceGrpc.BindService(new TestServiceImpl()));
 
-            string addr = "0.0.0.0:" + options.port;
+            string host = "0.0.0.0";
+            int port = options.port.Value;
             if (options.useTls)
             {
-                server.AddListeningPort(addr, TestCredentials.CreateTestServerCredentials());
+                server.AddListeningPort(host, port, TestCredentials.CreateTestServerCredentials());
             }
             else
             {
-                server.AddListeningPort(addr);
+                server.AddListeningPort(host, options.port.Value);
             }
-            Console.WriteLine("Running server on " + addr);
+            Console.WriteLine("Running server on " + string.Format("{0}:{1}", host, port));
             server.Start();
 
             server.ShutdownTask.Wait();
diff --git a/src/csharp/Grpc.IntegrationTesting/TestServiceGrpc.cs b/src/csharp/Grpc.IntegrationTesting/TestServiceGrpc.cs
index d1f8aa12c7..9f14dad6c0 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestServiceGrpc.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestServiceGrpc.cs
@@ -171,17 +171,17 @@ namespace grpc.testing
         // server-side interface
         public interface ITestService
         {
-            Task<Empty> EmptyCall(Empty request);
+            Task<Empty> EmptyCall(ServerCallContext context, Empty request);
 
-            Task<SimpleResponse> UnaryCall(SimpleRequest request);
+            Task<SimpleResponse> UnaryCall(ServerCallContext context, SimpleRequest request);
 
-            Task StreamingOutputCall(StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
+            Task StreamingOutputCall(ServerCallContext context, StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
 
-            Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream);
+            Task<StreamingInputCallResponse> StreamingInputCall(ServerCallContext context, IAsyncStreamReader<StreamingInputCallRequest> requestStream);
 
-            Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
+            Task FullDuplexCall(ServerCallContext context, IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
 
-            Task HalfDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
+            Task HalfDuplexCall(ServerCallContext context, IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream);
         }
 
         public static ServerServiceDefinition BindService(ITestService serviceImpl)
diff --git a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
index 8b0cf3a2d0..40f32b5a88 100644
--- a/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
+++ b/src/csharp/Grpc.IntegrationTesting/TestServiceImpl.cs
@@ -46,19 +46,19 @@ namespace grpc.testing
     /// </summary>
     public class TestServiceImpl : TestServiceGrpc.ITestService
     {
-        public Task<Empty> EmptyCall(Empty request)
+        public Task<Empty> EmptyCall(ServerCallContext context, Empty request)
         {
             return Task.FromResult(Empty.DefaultInstance);
         }
 
-        public Task<SimpleResponse> UnaryCall(SimpleRequest request)
+        public Task<SimpleResponse> UnaryCall(ServerCallContext context, SimpleRequest request)
         {
             var response = SimpleResponse.CreateBuilder()
                 .SetPayload(CreateZerosPayload(request.ResponseSize)).Build();
             return Task.FromResult(response);
         }
 
-        public async Task StreamingOutputCall(StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
+        public async Task StreamingOutputCall(ServerCallContext context, StreamingOutputCallRequest request, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
         {
             foreach (var responseParam in request.ResponseParametersList)
             {
@@ -68,7 +68,7 @@ namespace grpc.testing
             }
         }
 
-        public async Task<StreamingInputCallResponse> StreamingInputCall(IAsyncStreamReader<StreamingInputCallRequest> requestStream)
+        public async Task<StreamingInputCallResponse> StreamingInputCall(ServerCallContext context, IAsyncStreamReader<StreamingInputCallRequest> requestStream)
         {
             int sum = 0;
             await requestStream.ForEach(async request =>
@@ -78,7 +78,7 @@ namespace grpc.testing
             return StreamingInputCallResponse.CreateBuilder().SetAggregatedPayloadSize(sum).Build();
         }
 
-        public async Task FullDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
+        public async Task FullDuplexCall(ServerCallContext context, IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
         {
             await requestStream.ForEach(async request =>
             {
@@ -91,7 +91,7 @@ namespace grpc.testing
             });
         }
 
-        public async Task HalfDuplexCall(IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
+        public async Task HalfDuplexCall(ServerCallContext context, IAsyncStreamReader<StreamingOutputCallRequest> requestStream, IServerStreamWriter<StreamingOutputCallResponse> responseStream)
         {
             throw new NotImplementedException();
         }