private static void EndFastCopyTo <T>(IAsyncResult fastCopyToResult)
        {
            ExecutionState <T> executionState = (ExecutionState <T>)fastCopyToResult.AsyncState;

            try
            {
                executionState.UpdateCompletedSynchronously(fastCopyToResult.CompletedSynchronously);

                MultiBufferMemoryStream multiBufferMemoryStream = (MultiBufferMemoryStream)executionState.RestCMD.SendStream;
                multiBufferMemoryStream.EndFastCopyTo(fastCopyToResult);

                Executor.EndSendStreamCopy(executionState);
            }
            catch (Exception ex)
            {
                Logger.LogWarning(executionState.OperationContext, SR.TraceUploadError, ex.Message);
                executionState.ExceptionRef = ExecutorBase.TranslateExceptionBasedOnParseError(ex, executionState.Cmd.CurrentResult, executionState.Resp, executionState.Cmd.ParseError);
                Executor.EndOperation(executionState);
            }
        }