wire passing of C# CallFlags to C core
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index da45c48..1f738a3 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -106,7 +106,7 @@
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 using (var ctx = BatchContextSafeHandle.Create())
                 {
-                    call.StartUnary(ctx, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartUnary(ctx, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
 
                     var ev = cq.Pluck(ctx.Handle);
 
@@ -150,7 +150,7 @@
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartUnary(HandleUnaryResponse, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartUnary(HandleUnaryResponse, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
                 }
                 return unaryResponseTcs.Task;
             }
@@ -174,7 +174,7 @@
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartClientStreaming(HandleUnaryResponse, metadataArray);
+                    call.StartClientStreaming(HandleUnaryResponse, metadataArray, details.Options.Flags);
                 }
 
                 return unaryResponseTcs.Task;
@@ -200,7 +200,7 @@
                 streamingResponseCallFinishedTcs = new TaskCompletionSource<object>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartServerStreaming(HandleFinished, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartServerStreaming(HandleFinished, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
                 }
                 call.StartReceiveInitialMetadata(HandleReceivedResponseHeaders);
             }
@@ -222,7 +222,7 @@
                 streamingResponseCallFinishedTcs = new TaskCompletionSource<object>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartDuplexStreaming(HandleFinished, metadataArray);
+                    call.StartDuplexStreaming(HandleFinished, metadataArray, details.Options.Flags);
                 }
                 call.StartReceiveInitialMetadata(HandleReceivedResponseHeaders);
             }
diff --git a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
index f817a61..6bfcc7f 100644
--- a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
@@ -63,50 +63,50 @@
             Native.grpcsharp_call_set_credentials(this, credentials).CheckOk();
         }
 
-        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient(), context.GetReceivedMessage(), context.GetReceivedInitialMetadata()));
-                Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
+                Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags)
                     .CheckOk();
             }
         }
 
-        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
-            Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
+            Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags)
                 .CheckOk();
         }
 
-        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient(), context.GetReceivedMessage(), context.GetReceivedInitialMetadata()));
-                Native.grpcsharp_call_start_client_streaming(this, ctx, metadataArray).CheckOk();
+                Native.grpcsharp_call_start_client_streaming(this, ctx, metadataArray, callFlags).CheckOk();
             }
         }
 
-        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient()));
-                Native.grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags).CheckOk();
+                Native.grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags).CheckOk();
             }
         }
 
-        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient()));
-                Native.grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray).CheckOk();
+                Native.grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray, callFlags).CheckOk();
             }
         }
 
diff --git a/src/csharp/Grpc.Core/Internal/INativeCall.cs b/src/csharp/Grpc.Core/Internal/INativeCall.cs
index cd3719c..94fbb08 100644
--- a/src/csharp/Grpc.Core/Internal/INativeCall.cs
+++ b/src/csharp/Grpc.Core/Internal/INativeCall.cs
@@ -31,6 +31,7 @@
 #endregion
 
 using System;
+using Grpc.Core;
 
 namespace Grpc.Core.Internal
 {
@@ -54,19 +55,19 @@
     {
         void Cancel();
 
-        void CancelWithStatus(Grpc.Core.Status status);
+        void CancelWithStatus(Status status);
 
         string GetPeer();
 
-        void StartUnary(UnaryResponseClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartUnary(UnaryResponseClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartUnary(BatchContextSafeHandle ctx, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray);
+        void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray);
+        void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
         void StartReceiveMessage(ReceivedMessageHandler callback);
 
@@ -74,11 +75,11 @@
 
         void StartSendInitialMetadata(SendCompletionHandler callback, MetadataArraySafeHandle metadataArray);
 
-        void StartSendMessage(SendCompletionHandler callback, byte[] payload, Grpc.Core.WriteFlags writeFlags, bool sendEmptyInitialMetadata);
+        void StartSendMessage(SendCompletionHandler callback, byte[] payload, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
 
         void StartSendCloseFromClient(SendCompletionHandler callback);
 
-        void StartSendStatusFromServer(SendCompletionHandler callback, Grpc.Core.Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata, byte[] optionalPayload, Grpc.Core.WriteFlags writeFlags);
+        void StartSendStatusFromServer(SendCompletionHandler callback, Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata, byte[] optionalPayload, 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 40ba7e3..ce38e37 100644
--- a/src/csharp/Grpc.Core/Internal/NativeMethods.cs
+++ b/src/csharp/Grpc.Core/Internal/NativeMethods.cs
@@ -325,14 +325,14 @@
             public delegate CallError grpcsharp_call_cancel_delegate(CallSafeHandle call);
             public delegate CallError grpcsharp_call_cancel_with_status_delegate(CallSafeHandle call, StatusCode status, string description);
             public delegate CallError grpcsharp_call_start_unary_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_client_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_server_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen,
-                MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags,
+                MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_duplex_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_send_message_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
             public delegate CallError grpcsharp_call_send_close_from_client_delegate(CallSafeHandle call,