3 files changed, 46 insertions, 12 deletions

diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index cc37267161..016e1b8587 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -258,9 +258,19 @@ namespace Grpc.Core.Internal
             lock (myLock)
             {
                 GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
-                CheckSendingAllowed();
+                CheckSendingAllowed(allowFinished: true);
 
-                call.StartSendCloseFromClient(HandleHalfclosed);
+                if (!disposed && !finished)
+                {
+                    call.StartSendCloseFromClient(HandleSendCloseFromClientFinished);
+                }
+                else
+                {
+                    // In case the call has already been finished by the serverside,
+                    // the halfclose has already been done implicitly, so we only
+                    // emit the notification for the completion delegate.
+                    Task.Run(() => HandleSendCloseFromClientFinished(true));
+                }
 
                 halfcloseRequested = true;
                 sendCompletionDelegate = completionDelegate;
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
index aa5765be6f..ccd047f469 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallBase.cs
@@ -136,7 +136,7 @@ namespace Grpc.Core.Internal
             lock (myLock)
             {
                 GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
-                CheckSendingAllowed();
+                CheckSendingAllowed(allowFinished: false);
 
                 call.StartSendMessage(HandleSendFinished, payload, writeFlags, !initialMetadataSent);
 
@@ -202,14 +202,14 @@ namespace Grpc.Core.Internal
         {
         }
 
-        protected void CheckSendingAllowed()
+        protected void CheckSendingAllowed(bool allowFinished)
         {
             GrpcPreconditions.CheckState(started);
             CheckNotCancelled();
-            GrpcPreconditions.CheckState(!disposed);
+            GrpcPreconditions.CheckState(!disposed || allowFinished);
 
             GrpcPreconditions.CheckState(!halfcloseRequested, "Already halfclosed.");
-            GrpcPreconditions.CheckState(!finished, "Already finished.");
+            GrpcPreconditions.CheckState(!finished || allowFinished, "Already finished.");
             GrpcPreconditions.CheckState(sendCompletionDelegate == null, "Only one write can be pending at a time");
         }
 
@@ -294,9 +294,33 @@ namespace Grpc.Core.Internal
         }
 
         /// <summary>
-        /// Handles halfclose completion.
+        /// Handles halfclose (send close from client) completion.
+        /// </summary>
+        protected void HandleSendCloseFromClientFinished(bool success)
+        {
+            AsyncCompletionDelegate<object> origCompletionDelegate = null;
+            lock (myLock)
+            {
+                origCompletionDelegate = sendCompletionDelegate;
+                sendCompletionDelegate = null;
+
+                ReleaseResourcesIfPossible();
+            }
+
+            if (!success)
+            {
+                FireCompletion(origCompletionDelegate, null, new InvalidOperationException("Sending close from client has failed."));
+            }
+            else
+            {
+                FireCompletion(origCompletionDelegate, null, null);
+            }
+        }
+
+        /// <summary>
+        /// Handles send status from server completion.
         /// </summary>
-        protected void HandleHalfclosed(bool success)
+        protected void HandleSendStatusFromServerFinished(bool success)
         {
             AsyncCompletionDelegate<object> origCompletionDelegate = null;
             lock (myLock)
@@ -309,7 +333,7 @@ namespace Grpc.Core.Internal
 
             if (!success)
             {
-                FireCompletion(origCompletionDelegate, null, new InvalidOperationException("Halfclose failed"));
+                FireCompletion(origCompletionDelegate, null, new InvalidOperationException("Error sending status from server."));
             }
             else
             {
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
index e749448565..bea2b3660c 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCallServer.cs
@@ -113,7 +113,7 @@ namespace Grpc.Core.Internal
 
                 GrpcPreconditions.CheckState(!initialMetadataSent, "Response headers can only be sent once per call.");
                 GrpcPreconditions.CheckState(streamingWritesCounter == 0, "Response headers can only be sent before the first write starts.");
-                CheckSendingAllowed();
+                CheckSendingAllowed(allowFinished: false);
 
                 GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
 
@@ -137,11 +137,11 @@ namespace Grpc.Core.Internal
             lock (myLock)
             {
                 GrpcPreconditions.CheckNotNull(completionDelegate, "Completion delegate cannot be null");
-                CheckSendingAllowed();
+                CheckSendingAllowed(allowFinished: false);
 
                 using (var metadataArray = MetadataArraySafeHandle.Create(trailers))
                 {
-                    call.StartSendStatusFromServer(HandleHalfclosed, status, metadataArray, !initialMetadataSent);
+                    call.StartSendStatusFromServer(HandleSendStatusFromServerFinished, status, metadataArray, !initialMetadataSent);
                 }
                 halfcloseRequested = true;
                 readingDone = true;