override in benchmark

src/csharp/Grpc.Core/Internal/NativeMethods.cs

@@ -437,7 +437,7 @@ namespace Grpc.Core.Internal
 
             public delegate CallError grpcsharp_test_callback_delegate([MarshalAs(UnmanagedType.FunctionPtr)] OpCompletionDelegate callback);
             public delegate IntPtr grpcsharp_test_nop_delegate(IntPtr ptr);
-            public delegate void grpcsharp_test_override_method(string methodName, string variant);
+            public delegate void grpcsharp_test_override_method_delegate(string methodName, string variant);
         }
     }
 }

src/csharp/Grpc.Microbenchmarks/SendMessageBenchmark.cs

@@ -83,7 +83,7 @@ namespace Grpc.Microbenchmarks
             {
                 call.StartSendMessage(sendCompletionHandler, payload, writeFlags, false);
                 var callback = completionRegistry.Extract(completionRegistry.LastRegisteredKey);
-                callback();
+                callback(true);
             }
             stopwatch.Stop();
             Console.WriteLine("Elapsed millis: " + stopwatch.ElapsedMilliseconds);