added WriteOptions support and enabled NoCompress flag to be used for all writes

14 files changed, 376 insertions, 93 deletions

diff --git a/src/csharp/Grpc.Core/CallOptions.cs b/src/csharp/Grpc.Core/CallOptions.cs
index 8e9739335f..e8d0b0647f 100644
--- a/src/csharp/Grpc.Core/CallOptions.cs
+++ b/src/csharp/Grpc.Core/CallOptions.cs
@@ -47,6 +47,7 @@ namespace Grpc.Core
         readonly Metadata headers;
         readonly DateTime deadline;
         readonly CancellationToken cancellationToken;
+        readonly WriteOptions writeOptions;
 
         /// <summary>
         /// Creates a new instance of <c>CallOptions</c>.
@@ -54,10 +55,12 @@ namespace Grpc.Core
         /// <param name="headers">Headers to be sent with the call.</param>
         /// <param name="deadline">Deadline for the call to finish. null means no deadline.</param>
         /// <param name="cancellationToken">Can be used to request cancellation of the call.</param>
-        public CallOptions(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken))
+        /// <param name="writeOptions">Write options that will be used for this call.</param>
+        public CallOptions(Metadata headers = null, DateTime? deadline = null, CancellationToken cancellationToken = default(CancellationToken), WriteOptions writeOptions = null)
         {
             // TODO(jtattermusch): consider only creating metadata object once it's really needed.
             this.headers = headers != null ? headers : new Metadata();
+            // TODO(jtattermusch): allow null value of deadline?
             this.deadline = deadline.HasValue ? deadline.Value : DateTime.MaxValue;
             this.cancellationToken = cancellationToken;
         }
@@ -85,5 +88,16 @@ namespace Grpc.Core
         {
             get { return cancellationToken; }
         }
+
+        /// <summary>
+        /// Write options that will be used for this call.
+        /// </summary>
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return this.writeOptions;
+            }
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/CompressionLevel.cs b/src/csharp/Grpc.Core/CompressionLevel.cs
new file mode 100644
index 0000000000..399652b85e
--- /dev/null
+++ b/src/csharp/Grpc.Core/CompressionLevel.cs
@@ -0,0 +1,63 @@
+#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;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Compression level based on grpc_compression_level from grpc/compression.h
+    /// </summary>
+    public enum CompressionLevel
+    {
+        /// <summary>
+        /// No compression.
+        /// </summary>
+        None = 0,
+
+        /// <summary>
+        /// Low compression.
+        /// </summary>
+        Low,
+
+        /// <summary>
+        /// Medium compression.
+        /// </summary>
+        Medium,
+
+        /// <summary>
+        /// High compression.
+        /// </summary>
+        High,
+    }
+}
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 52defd1965..0616ed9f3e 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -115,6 +115,8 @@
     <Compile Include="ChannelState.cs" />
     <Compile Include="CallInvocationDetails.cs" />
     <Compile Include="CallOptions.cs" />
+    <Compile Include="CompressionLevel.cs" />
+    <Compile Include="WriteOptions.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.nuspec" />
diff --git a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
index 2000210252..b554b6e266 100644
--- a/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
+++ b/src/csharp/Grpc.Core/IAsyncStreamWriter.cs
@@ -50,5 +50,17 @@ namespace Grpc.Core
         /// </summary>
         /// <param name="message">the message to be written. Cannot be null.</param>
         Task WriteAsync(T message);
+
+        /// <summary>
+        /// Write options that will be used for the next write.
+        /// If null, default options will be used.
+        /// Once set, this property maintains its value across subsequent
+        /// writes.
+        /// Internally, closing the stream is on client and sending
+        /// status from server is treated as a write, so write options
+        /// are also applied to these operations.
+        /// </summary>
+        /// <value>The write options.</value>
+        WriteOptions WriteOptions { get; set; }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index 414b5c4282..c26b0773ba 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -50,7 +50,7 @@ namespace Grpc.Core.Internal
     {
         static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<AsyncCall<TRequest, TResponse>>();
 
-        readonly CallInvocationDetails<TRequest, TResponse> callDetails;
+        readonly CallInvocationDetails<TRequest, TResponse> details;
 
         // Completion of a pending unary response if not null.
         TaskCompletionSource<TResponse> unaryResponseTcs;
@@ -63,7 +63,7 @@ namespace Grpc.Core.Internal
         public AsyncCall(CallInvocationDetails<TRequest, TResponse> callDetails)
             : base(callDetails.RequestMarshaller.Serializer, callDetails.ResponseMarshaller.Deserializer)
         {
-            this.callDetails = callDetails;
+            this.details = callDetails;
         }
 
         // TODO: this method is not Async, so it shouldn't be in AsyncCall class, but 
@@ -89,11 +89,11 @@ namespace Grpc.Core.Internal
                     readingDone = true;
                 }
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
                     using (var ctx = BatchContextSafeHandle.Create())
                     {
-                        call.StartUnary(payload, ctx, metadataArray);
+                        call.StartUnary(ctx, payload, metadataArray, GetWriteFlagsForCall());
                         var ev = cq.Pluck(ctx.Handle);
 
                         bool success = (ev.success != 0);
@@ -130,7 +130,7 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 halfcloseRequested = true;
                 readingDone = true;
@@ -138,9 +138,9 @@ namespace Grpc.Core.Internal
                 byte[] payload = UnsafeSerialize(msg);
 
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartUnary(payload, HandleUnaryResponse, metadataArray);
+                    call.StartUnary(HandleUnaryResponse, payload, metadataArray, GetWriteFlagsForCall());
                 }
                 return unaryResponseTcs.Task;
             }
@@ -157,14 +157,14 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 readingDone = true;
 
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartClientStreaming(HandleUnaryResponse, metadataArray);
+                    call.StartClientStreaming(HandleUnaryResponse, metadataArray, GetWriteFlagsForCall());
                 }
 
                 return unaryResponseTcs.Task;
@@ -181,16 +181,16 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
                 halfcloseRequested = true;
                 halfclosed = true;  // halfclose not confirmed yet, but it will be once finishedHandler is called.
 
                 byte[] payload = UnsafeSerialize(msg);
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartServerStreaming(payload, HandleFinished, metadataArray);
+                    call.StartServerStreaming(HandleFinished, payload, metadataArray, GetWriteFlagsForCall());
                 }
             }
         }
@@ -206,11 +206,11 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckState(!started);
                 started = true;
 
-                Initialize(callDetails.Channel.Environment.CompletionQueue);
+                Initialize(details.Channel.Environment.CompletionQueue);
 
-                using (var metadataArray = MetadataArraySafeHandle.Create(callDetails.Options.Headers))
+                using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartDuplexStreaming(HandleFinished, metadataArray);
+                    call.StartDuplexStreaming(HandleFinished, metadataArray, GetWriteFlagsForCall());
                 }
             }
         }
@@ -219,9 +219,9 @@ namespace Grpc.Core.Internal
         /// Sends a streaming request. Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendMessage(TRequest msg, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendMessage(TRequest msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
-            StartSendMessageInternal(msg, completionDelegate);
+            StartSendMessageInternal(msg, writeFlags, completionDelegate);
         }
 
         /// <summary>
@@ -238,14 +238,14 @@ namespace Grpc.Core.Internal
         /// Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendCloseFromClient(AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendCloseFromClient(WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
             lock (myLock)
             {
                 Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
-                call.StartSendCloseFromClient(HandleHalfclosed);
+                call.StartSendCloseFromClient(HandleHalfclosed, writeFlags);
 
                 halfcloseRequested = true;
                 sendCompletionDelegate = completionDelegate;
@@ -278,6 +278,14 @@ namespace Grpc.Core.Internal
             }
         }
 
+        public CallInvocationDetails<TRequest, TResponse>  Details
+        {
+            get
+            {
+                return this.details;
+            }
+        }
+
         /// <summary>
         /// On client-side, we only fire readCompletionDelegate once all messages have been read 
         /// and status has been received.
@@ -310,14 +318,14 @@ namespace Grpc.Core.Internal
 
         protected override void OnReleaseResources()
         {
-            callDetails.Channel.Environment.DebugStats.ActiveClientCalls.Decrement();
+            details.Channel.Environment.DebugStats.ActiveClientCalls.Decrement();
         }
 
         private void Initialize(CompletionQueueSafeHandle cq)
         {
-            var call = callDetails.Channel.Handle.CreateCall(callDetails.Channel.Environment.CompletionRegistry, cq,
-                callDetails.Method, callDetails.Host, Timespec.FromDateTime(callDetails.Options.Deadline));
-            callDetails.Channel.Environment.DebugStats.ActiveClientCalls.Increment();
+            var call = details.Channel.Handle.CreateCall(details.Channel.Environment.CompletionRegistry, cq,
+                details.Method, details.Host, Timespec.FromDateTime(details.Options.Deadline));
+            details.Channel.Environment.DebugStats.ActiveClientCalls.Increment();
             InitializeInternal(call);
             RegisterCancellationCallback();
         }
@@ -325,7 +333,7 @@ namespace Grpc.Core.Internal
         // Make sure that once cancellationToken for this call is cancelled, Cancel() will be called.
         private void RegisterCancellationCallback()
         {
-            var token = callDetails.Options.CancellationToken;
+            var token = details.Options.CancellationToken;
             if (token.CanBeCanceled)
             {
                 token.Register(() => this.Cancel());
@@ -333,6 +341,15 @@ namespace Grpc.Core.Internal
         }
 
         /// <summary>
+        /// Gets WriteFlags set in callDetails.Options.WriteOptions
+        /// </summary>
+        private WriteFlags GetWriteFlagsForCall()
+        {
+            var writeOptions = details.Options.WriteOptions;
+            return writeOptions != null ? writeOptions.Flags : default(WriteFlags);
+        }
+
+        /// <summary>
         /// Handler for unary response completion.
         /// </summary>
         private void HandleUnaryResponse(bool success, BatchContextSafeHandle ctx)
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
index 38f2a5baeb..0c7694e9a5 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
@@ -123,7 +123,7 @@ namespace Grpc.Core.Internal
         /// Initiates sending a message. Only one send operation can be active at a time.
         /// completionDelegate is invoked upon completion.
         /// </summary>
-        protected void StartSendMessageInternal(TWrite msg, AsyncCompletionDelegate<object> completionDelegate)
+        protected void StartSendMessageInternal(TWrite msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
             byte[] payload = UnsafeSerialize(msg);
 
@@ -132,7 +132,7 @@ namespace Grpc.Core.Internal
                 Preconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
                 CheckSendingAllowed();
 
-                call.StartSendMessage(payload, HandleSendFinished);
+                call.StartSendMessage(HandleSendFinished, payload, writeFlags);
                 sendCompletionDelegate = completionDelegate;
             }
         }
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index 513902ee36..8d7bdf65aa 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -83,9 +83,9 @@ namespace Grpc.Core.Internal
         /// Sends a streaming response. Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendMessage(TResponse msg, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendMessage(TResponse msg, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
-            StartSendMessageInternal(msg, completionDelegate);
+            StartSendMessageInternal(msg, writeFlags, completionDelegate);
         }
 
         /// <summary>
@@ -102,7 +102,7 @@ namespace Grpc.Core.Internal
         /// Only one pending send action is allowed at any given time.
         /// completionDelegate is called when the operation finishes.
         /// </summary>
-        public void StartSendStatusFromServer(Status status, Metadata trailers, AsyncCompletionDelegate<object> completionDelegate)
+        public void StartSendStatusFromServer(Status status, Metadata trailers, WriteFlags writeFlags, AsyncCompletionDelegate<object> completionDelegate)
         {
             lock (myLock)
             {
@@ -111,7 +111,7 @@ namespace Grpc.Core.Internal
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
                 {
-                    call.StartSendStatusFromServer(status, HandleHalfclosed, metadataArray);
+                    call.StartSendStatusFromServer(HandleHalfclosed, status, metadataArray, writeFlags);
                 }
                 halfcloseRequested = true;
                 readingDone = true;
diff --git a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
index 714749b171..be1426feb4 100644
--- a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
@@ -53,32 +53,32 @@ namespace Grpc.Core.Internal
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_unary(CallSafeHandle call,
-            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_client_streaming(CallSafeHandle call,
-            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_server_streaming(CallSafeHandle call,
             BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len,
-            MetadataArraySafeHandle metadataArray);
+            MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_start_duplex_streaming(CallSafeHandle call,
-            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_message(CallSafeHandle call,
-            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len);
+            BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_close_from_client(CallSafeHandle call,
-            BatchContextSafeHandle ctx);
+            BatchContextSafeHandle ctx, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_send_status_from_server(CallSafeHandle call, 
-            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray);
+            BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
         [DllImport("grpc_csharp_ext.dll")]
         static extern GRPCCallError grpcsharp_call_recv_message(CallSafeHandle call,
@@ -89,6 +89,10 @@ namespace Grpc.Core.Internal
             BatchContextSafeHandle ctx);
 
         [DllImport("grpc_csharp_ext.dll")]
+        static extern GRPCCallError grpcsharp_call_send_initial_metadata(CallSafeHandle call,
+            BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+
+        [DllImport("grpc_csharp_ext.dll")]
         static extern CStringSafeHandle grpcsharp_call_get_peer(CallSafeHandle call);
 
         [DllImport("grpc_csharp_ext.dll")]
@@ -103,60 +107,60 @@ namespace Grpc.Core.Internal
             this.completionRegistry = completionRegistry;
         }
 
-        public void StartUnary(byte[] payload, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartUnary(BatchCompletionDelegate callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray)
+            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
                 .CheckOk();
         }
 
-        public void StartUnary(byte[] payload, BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray)
+        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
-            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray)
+            grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
                 .CheckOk();
         }
 
-        public void StartClientStreaming(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartClientStreaming(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_client_streaming(this, ctx, metadataArray).CheckOk();
+            grpcsharp_call_start_client_streaming(this, ctx, metadataArray, writeFlags).CheckOk();
         }
 
-        public void StartServerStreaming(byte[] payload, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartServerStreaming(BatchCompletionDelegate callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray).CheckOk();
+            grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags).CheckOk();
         }
 
-        public void StartDuplexStreaming(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartDuplexStreaming(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray).CheckOk();
+            grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray, writeFlags).CheckOk();
         }
 
-        public void StartSendMessage(byte[] payload, BatchCompletionDelegate callback)
+        public void StartSendMessage(BatchCompletionDelegate callback, byte[] payload, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_message(this, ctx, payload, new UIntPtr((ulong)payload.Length)).CheckOk();
+            grpcsharp_call_send_message(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags).CheckOk();
         }
 
-        public void StartSendCloseFromClient(BatchCompletionDelegate callback)
+        public void StartSendCloseFromClient(BatchCompletionDelegate callback, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_close_from_client(this, ctx).CheckOk();
+            grpcsharp_call_send_close_from_client(this, ctx, writeFlags).CheckOk();
         }
 
-        public void StartSendStatusFromServer(Status status, BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray)
+        public void StartSendStatusFromServer(BatchCompletionDelegate callback, Status status, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
         {
             var ctx = BatchContextSafeHandle.Create();
             completionRegistry.RegisterBatchCompletion(ctx, callback);
-            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray).CheckOk();
+            grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray, writeFlags).CheckOk();
         }
 
         public void StartReceiveMessage(BatchCompletionDelegate callback)
@@ -173,6 +177,13 @@ namespace Grpc.Core.Internal
             grpcsharp_call_start_serverside(this, ctx).CheckOk();
         }
 
+        public void SendInitialMetadata(BatchCompletionDelegate callback, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        {
+            var ctx = BatchContextSafeHandle.Create();
+            completionRegistry.RegisterBatchCompletion(ctx, callback);
+            grpcsharp_call_send_initial_metadata(this, ctx, metadataArray, writeFlags).CheckOk();
+        }
+
         public void Cancel()
         {
             grpcsharp_call_cancel(this).CheckOk();
diff --git a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
index 58f493463b..4a14694977 100644
--- a/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ClientRequestStream.cs
@@ -40,24 +40,44 @@ namespace Grpc.Core.Internal
     internal class ClientRequestStream<TRequest, TResponse> : IClientStreamWriter<TRequest>
     {
         readonly AsyncCall<TRequest, TResponse> call;
+        WriteOptions writeOptions;
 
         public ClientRequestStream(AsyncCall<TRequest, TResponse> call)
         {
             this.call = call;
+            this.writeOptions = call.Details.Options.WriteOptions;
         }
 
         public Task WriteAsync(TRequest message)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendMessage(message, taskSource.CompletionDelegate);
+            call.StartSendMessage(message, GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
 
         public Task CompleteAsync()
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendCloseFromClient(taskSource.CompletionDelegate);
+            call.StartSendCloseFromClient(GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
+
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return this.writeOptions;
+            }
+            set
+            {
+                writeOptions = value;
+            }
+        }
+
+        private WriteFlags GetWriteFlags()
+        {
+            var options = writeOptions;
+            return options != null ? options.Flags : default(WriteFlags);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
index 19f0e3c57f..34db03cc38 100644
--- a/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerCallHandler.cs
@@ -75,7 +75,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
@@ -131,7 +131,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 Preconditions.CheckArgument(await requestStream.MoveNext());
@@ -187,7 +187,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 var result = await handler(requestStream, context);
@@ -247,7 +247,7 @@ namespace Grpc.Core.Internal
             var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);
 
             Status status;
-            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, asyncCall.CancellationToken);
+            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
             try
             {
                 await handler(requestStream, responseStream, context);
@@ -304,13 +304,13 @@ namespace Grpc.Core.Internal
             return new Status(StatusCode.Unknown, "Exception was thrown by handler.");
         }
 
-        public static ServerCallContext NewContext(ServerRpcNew newRpc, string peer, CancellationToken cancellationToken)
+        public static ServerCallContext NewContext(ServerRpcNew newRpc, string peer, IHasWriteOptions writeOptionsHolder, CancellationToken cancellationToken)
         {
             DateTime realtimeDeadline = newRpc.Deadline.ToClockType(GPRClockType.Realtime).ToDateTime();
 
             return new ServerCallContext(
                 newRpc.Method, newRpc.Host, peer, realtimeDeadline,
-                newRpc.RequestMetadata, cancellationToken);
+                newRpc.RequestMetadata, cancellationToken, writeOptionsHolder);
         }
     }
 }
diff --git a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
index 756dcee87f..1d79241f77 100644
--- a/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
+++ b/src/csharp/Grpc.Core/Internal/ServerResponseStream.cs
@@ -38,11 +38,12 @@ namespace Grpc.Core.Internal
     /// <summary>
     /// Writes responses asynchronously to an underlying AsyncCallServer object.
     /// </summary>
-    internal class ServerResponseStream<TRequest, TResponse> : IServerStreamWriter<TResponse>
+    internal class ServerResponseStream<TRequest, TResponse> : IServerStreamWriter<TResponse>, IHasWriteOptions
         where TRequest : class
         where TResponse : class
     {
         readonly AsyncCallServer<TRequest, TResponse> call;
+        WriteOptions writeOptions;
 
         public ServerResponseStream(AsyncCallServer<TRequest, TResponse> call)
         {
@@ -52,15 +53,33 @@ namespace Grpc.Core.Internal
         public Task WriteAsync(TResponse message)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendMessage(message, taskSource.CompletionDelegate);
+            call.StartSendMessage(message, GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
 
         public Task WriteStatusAsync(Status status, Metadata trailers)
         {
             var taskSource = new AsyncCompletionTaskSource<object>();
-            call.StartSendStatusFromServer(status, trailers, taskSource.CompletionDelegate);
+            call.StartSendStatusFromServer(status, trailers, GetWriteFlags(), taskSource.CompletionDelegate);
             return taskSource.Task;
         }
+
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return writeOptions;
+            }
+            set
+            {
+                writeOptions = value;
+            }
+        }
+
+        private WriteFlags GetWriteFlags()
+        {
+            var options = writeOptions;
+            return options != null ? options.Flags : default(WriteFlags);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core/ServerCallContext.cs b/src/csharp/Grpc.Core/ServerCallContext.cs
index 032b1390db..5657eb8513 100644
--- a/src/csharp/Grpc.Core/ServerCallContext.cs
+++ b/src/csharp/Grpc.Core/ServerCallContext.cs
@@ -36,6 +36,8 @@ using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 
+using Grpc.Core.Internal;
+
 namespace Grpc.Core
 {
     /// <summary>
@@ -54,8 +56,9 @@ namespace Grpc.Core
         private readonly Metadata responseTrailers = new Metadata();
 
         private Status status = Status.DefaultSuccess;
+        private IHasWriteOptions writeOptionsHolder;
 
-        public ServerCallContext(string method, string host, string peer, DateTime deadline, Metadata requestHeaders, CancellationToken cancellationToken)
+        public ServerCallContext(string method, string host, string peer, DateTime deadline, Metadata requestHeaders, CancellationToken cancellationToken, IHasWriteOptions writeOptionsHolder)
         {
             this.method = method;
             this.host = host;
@@ -63,6 +66,7 @@ namespace Grpc.Core
             this.deadline = deadline;
             this.requestHeaders = requestHeaders;
             this.cancellationToken = cancellationToken;
+            this.writeOptionsHolder = writeOptionsHolder;
         }
             
         /// <summary>Name of method called in this RPC.</summary>
@@ -141,5 +145,30 @@ namespace Grpc.Core
                 status = value;
             }
         }
+
+        /// <summary>
+        /// Allows setting write options for the following write.
+        /// For streaming response calls, this property is also exposed as on IServerStreamWriter for convenience.
+        /// Both properties are backed by the same underlying value.
+        /// </summary>
+        public WriteOptions WriteOptions
+        {
+            get
+            {
+                return writeOptionsHolder.WriteOptions;
+            }
+            set
+            {
+                writeOptionsHolder.WriteOptions = value;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Allows sharing write options between ServerCallContext and other objects.
+    /// </summary>
+    public interface IHasWriteOptions
+    {
+        WriteOptions WriteOptions { get; set; }
     }
 }
diff --git a/src/csharp/Grpc.Core/WriteOptions.cs b/src/csharp/Grpc.Core/WriteOptions.cs
new file mode 100644
index 0000000000..ec4a7dd8cd
--- /dev/null
+++ b/src/csharp/Grpc.Core/WriteOptions.cs
@@ -0,0 +1,83 @@
+#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;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Flags for write operations.
+    /// </summary>
+    [Flags]
+    public enum WriteFlags
+    {
+        /// <summary>
+        /// Hint that the write may be buffered and need not go out on the wire immediately.
+        /// gRPC is free to buffer the message until the next non-buffered
+        /// write, or until write stream completion, but it need not buffer completely or at all.
+        /// </summary>
+        BufferHint = 0x1,
+
+        /// <summary>
+        /// Force compression to be disabled for a particular write.
+        /// </summary>
+        NoCompress = 0x2
+    }
+
+
+    /// <summary>
+    /// Options for write operations.
+    /// </summary>
+    public class WriteOptions
+    {
+        /// <summary>
+        /// Default write options.
+        /// </summary>
+        public static readonly WriteOptions Default = new WriteOptions();
+            
+        private WriteFlags flags;
+
+        public WriteOptions(WriteFlags flags = default(WriteFlags))
+        {
+            this.flags = flags;
+        }
+
+        public WriteFlags Flags
+        {
+            get
+            {
+                return this.flags;
+            }
+        }
+    }
+}
diff --git a/src/csharp/ext/grpc_csharp_ext.c b/src/csharp/ext/grpc_csharp_ext.c
index 048887bc12..165459371b 100644
--- a/src/csharp/ext/grpc_csharp_ext.c
+++ b/src/csharp/ext/grpc_csharp_ext.c
@@ -497,7 +497,7 @@ GPR_EXPORT void GPR_CALLTYPE grpcsharp_call_destroy(grpc_call *call) {
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
                            const char *send_buffer, size_t send_buffer_len,
-                           grpc_metadata_array *initial_metadata) {
+                           grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[6];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -506,15 +506,15 @@ grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   ops[1].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[1].data.send_message = ctx->send_message;
-  ops[1].flags = 0;
+  ops[1].flags = write_flags;
 
   ops[2].op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
-  ops[2].flags = 0;
+  ops[2].flags = write_flags;
 
   ops[3].op = GRPC_OP_RECV_INITIAL_METADATA;
   ops[3].data.recv_initial_metadata = &(ctx->recv_initial_metadata);
@@ -542,7 +542,7 @@ grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_client_streaming(grpc_call *call,
                                       grpcsharp_batch_context *ctx,
-                                      grpc_metadata_array *initial_metadata) {
+                                      grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[4];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -551,7 +551,7 @@ grpcsharp_call_start_client_streaming(grpc_call *call,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   ops[1].op = GRPC_OP_RECV_INITIAL_METADATA;
   ops[1].data.recv_initial_metadata = &(ctx->recv_initial_metadata);
@@ -578,7 +578,7 @@ grpcsharp_call_start_client_streaming(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
     grpc_call *call, grpcsharp_batch_context *ctx, const char *send_buffer,
-    size_t send_buffer_len, grpc_metadata_array *initial_metadata) {
+    size_t send_buffer_len, grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[5];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -587,15 +587,15 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   ops[1].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[1].data.send_message = ctx->send_message;
-  ops[1].flags = 0;
+  ops[1].flags = write_flags;
 
   ops[2].op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
-  ops[2].flags = 0;
+  ops[2].flags = write_flags;
 
   ops[3].op = GRPC_OP_RECV_INITIAL_METADATA;
   ops[3].data.recv_initial_metadata = &(ctx->recv_initial_metadata);
@@ -619,7 +619,7 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_duplex_streaming(grpc_call *call,
                                       grpcsharp_batch_context *ctx,
-                                      grpc_metadata_array *initial_metadata) {
+                                      grpc_metadata_array *initial_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[3];
   ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
@@ -628,7 +628,7 @@ grpcsharp_call_start_duplex_streaming(grpc_call *call,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   ops[1].op = GRPC_OP_RECV_INITIAL_METADATA;
   ops[1].data.recv_initial_metadata = &(ctx->recv_initial_metadata);
@@ -651,31 +651,31 @@ grpcsharp_call_start_duplex_streaming(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_send_message(grpc_call *call, grpcsharp_batch_context *ctx,
-                            const char *send_buffer, size_t send_buffer_len) {
+                            const char *send_buffer, size_t send_buffer_len, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[1];
   ops[0].op = GRPC_OP_SEND_MESSAGE;
   ctx->send_message = string_to_byte_buffer(send_buffer, send_buffer_len);
   ops[0].data.send_message = ctx->send_message;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
 }
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_send_close_from_client(grpc_call *call,
-                                      grpcsharp_batch_context *ctx) {
+                                      grpcsharp_batch_context *ctx, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[1];
   ops[0].op = GRPC_OP_SEND_CLOSE_FROM_CLIENT;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
 }
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_send_status_from_server(
     grpc_call *call, grpcsharp_batch_context *ctx, grpc_status_code status_code,
-    const char *status_details, grpc_metadata_array *trailing_metadata) {
+    const char *status_details, grpc_metadata_array *trailing_metadata, gpr_uint32 write_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[1];
   ops[0].op = GRPC_OP_SEND_STATUS_FROM_SERVER;
@@ -688,7 +688,7 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_send_status_from_server(
       ctx->send_status_from_server.trailing_metadata.count;
   ops[0].data.send_status_from_server.trailing_metadata =
       ctx->send_status_from_server.trailing_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = write_flags;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
 }
@@ -706,16 +706,29 @@ grpcsharp_call_recv_message(grpc_call *call, grpcsharp_batch_context *ctx) {
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_serverside(grpc_call *call, grpcsharp_batch_context *ctx) {
   /* TODO: don't use magic number */
-  grpc_op ops[2];
-  ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
-  ops[0].data.send_initial_metadata.count = 0;
-  ops[0].data.send_initial_metadata.metadata = NULL;
+  grpc_op ops[1];
+  ops[0].op = GRPC_OP_RECV_CLOSE_ON_SERVER;
+  ops[0].data.recv_close_on_server.cancelled =
+      (&ctx->recv_close_on_server_cancelled);
   ops[0].flags = 0;
 
-  ops[1].op = GRPC_OP_RECV_CLOSE_ON_SERVER;
-  ops[1].data.recv_close_on_server.cancelled =
-      (&ctx->recv_close_on_server_cancelled);
-  ops[1].flags = 0;
+  return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
+}
+
+GPR_EXPORT grpc_call_error GPR_CALLTYPE
+grpcsharp_call_send_initial_metadata(grpc_call *call,
+                                     grpcsharp_batch_context *ctx,
+                                     grpc_metadata_array *initial_metadata,
+                                     gpr_uint32 write_flags) {
+  /* TODO: don't use magic number */
+  grpc_op ops[1];
+  ops[0].op = GRPC_OP_SEND_INITIAL_METADATA;
+  grpcsharp_metadata_array_move(&(ctx->send_initial_metadata),
+                                initial_metadata);
+  ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
+  ops[0].data.send_initial_metadata.metadata =
+      ctx->send_initial_metadata.metadata;
+  ops[0].flags = write_flags;
 
   return grpc_call_start_batch(call, ops, sizeof(ops) / sizeof(ops[0]), ctx);
 }