private void BeginSendImpl(ServiceRequest request, ExecutionContext context, RetryableAsyncResult asyncResult)
        {
            if (asyncResult.InnerAsyncResult != null)
            {
                asyncResult.InnerAsyncResult.Dispose();
            }

            asyncResult.InnerAsyncResult = _innerClient.BeginSend(request, context, asyncResult.Callback, asyncResult) as AsyncResult;
        }