make SendStatusFromServer optionally send a message as well
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index eafe2cc..c5d900b 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -149,7 +149,8 @@
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
                 {
-                    call.StartSendStatusFromServer(HandleSendStatusFromServerFinished, status, metadataArray, !initialMetadataSent);
+                    call.StartSendStatusFromServer(HandleSendStatusFromServerFinished, status, metadataArray, !initialMetadataSent,
+                        null, new WriteFlags());
                 }
                 halfcloseRequested = true;
                 initialMetadataSent = true;
diff --git a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
index 500653b..244b97d 100644
--- a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
@@ -135,13 +135,16 @@
             }
         }
 
-        public void StartSendStatusFromServer(SendCompletionHandler callback, Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata)
+        public void StartSendStatusFromServer(SendCompletionHandler callback, Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata,
+            byte[] optionalPayload, WriteFlags writeFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
+                var optionalPayloadLength = optionalPayload != null ? new UIntPtr((ulong)optionalPayload.Length) : UIntPtr.Zero;
                 completionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success));
-                Native.grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray, sendEmptyInitialMetadata).CheckOk();
+                Native.grpcsharp_call_send_status_from_server(this, ctx, status.StatusCode, status.Detail, metadataArray, sendEmptyInitialMetadata,
+                    optionalPayload, optionalPayloadLength, writeFlags).CheckOk();
             }
         }
 
diff --git a/src/csharp/Grpc.Core/Internal/INativeCall.cs b/src/csharp/Grpc.Core/Internal/INativeCall.cs
index cbef599..cd3719c 100644
--- a/src/csharp/Grpc.Core/Internal/INativeCall.cs
+++ b/src/csharp/Grpc.Core/Internal/INativeCall.cs
@@ -78,7 +78,7 @@
 
         void StartSendCloseFromClient(SendCompletionHandler callback);
 
-        void StartSendStatusFromServer(SendCompletionHandler callback, Grpc.Core.Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata);
+        void StartSendStatusFromServer(SendCompletionHandler callback, Grpc.Core.Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata, byte[] optionalPayload, Grpc.Core.WriteFlags writeFlags);
 
         void StartServerSide(ReceivedCloseOnServerHandler callback);
     }
diff --git a/src/csharp/Grpc.Core/Internal/NativeMethods.cs b/src/csharp/Grpc.Core/Internal/NativeMethods.cs
index 9ee0ba3..c277c73 100644
--- a/src/csharp/Grpc.Core/Internal/NativeMethods.cs
+++ b/src/csharp/Grpc.Core/Internal/NativeMethods.cs
@@ -421,20 +421,21 @@
             public delegate GRPCCallError grpcsharp_call_cancel_delegate(CallSafeHandle call);
             public delegate GRPCCallError grpcsharp_call_cancel_with_status_delegate(CallSafeHandle call, StatusCode status, string description);
             public delegate GRPCCallError grpcsharp_call_start_unary_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
             public delegate GRPCCallError grpcsharp_call_start_client_streaming_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
             public delegate GRPCCallError grpcsharp_call_start_server_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len,
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen,
                 MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
             public delegate GRPCCallError grpcsharp_call_start_duplex_streaming_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
             public delegate GRPCCallError grpcsharp_call_send_message_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
             public delegate GRPCCallError grpcsharp_call_send_close_from_client_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx);
             public delegate GRPCCallError grpcsharp_call_send_status_from_server_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata);
+                BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata,
+                byte[] optionalSendBuffer, UIntPtr optionalSendBufferLen, WriteFlags writeFlags);
             public delegate GRPCCallError grpcsharp_call_recv_message_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx);
             public delegate GRPCCallError grpcsharp_call_recv_initial_metadata_delegate(CallSafeHandle call,
@@ -593,7 +594,7 @@
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_start_unary(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_start_client_streaming(CallSafeHandle call,
@@ -601,7 +602,7 @@
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_start_server_streaming(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len,
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen,
                 MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
 
             [DllImport("grpc_csharp_ext.dll")]
@@ -610,7 +611,7 @@
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_send_message(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] send_buffer, UIntPtr send_buffer_len, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_send_close_from_client(CallSafeHandle call,
@@ -618,7 +619,8 @@
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_send_status_from_server(CallSafeHandle call,
-                BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata);
+                BatchContextSafeHandle ctx, StatusCode statusCode, string statusMessage, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata,
+                byte[] optionalSendBuffer, UIntPtr optionalSendBufferLen, WriteFlags writeFlags);
 
             [DllImport("grpc_csharp_ext.dll")]
             public static extern GRPCCallError grpcsharp_call_recv_message(CallSafeHandle call,