System.Net.FtpWebRequest.BeginGetResponse C# (CSharp) Method

        public override IAsyncResult BeginGetResponse(AsyncCallback callback, object state)
        {
            if (NetEventSource.IsEnabled)
            {
                NetEventSource.Enter(this);
                NetEventSource.Info(this, $"Method: {_methodInfo.Method}");
            }

            ContextAwareResult asyncResult;

            try
            {
                if (_ftpWebResponse != null)
                {
                    asyncResult = new ContextAwareResult(this, state, callback);
                    asyncResult.InvokeCallback(_ftpWebResponse);
                    return asyncResult;
                }

                if (_getResponseStarted)
                {
                    throw new InvalidOperationException(SR.net_repcall);
                }

                _getResponseStarted = true;
                CheckError();

                RequestStage prev = FinishRequestStage(RequestStage.RequestStarted);
                asyncResult = new ContextAwareResult(true, true, this, state, callback);
                _readAsyncResult = asyncResult;

                if (prev >= RequestStage.RequestStarted)
                {
                    // To make sure the context is flowed
                    asyncResult.StartPostingAsyncOp();
                    asyncResult.FinishPostingAsyncOp();

                    if (prev >= RequestStage.ReadReady)
                        asyncResult = null;
                    else
                    {
                        lock (_syncObject)
                        {
                            if (_requestStage >= RequestStage.ReadReady)
                                asyncResult = null; ;
                        }
                    }

                    if (asyncResult == null)
                    {
                        // need to complete it now
                        asyncResult = (ContextAwareResult)_readAsyncResult;
                        if (!asyncResult.InternalPeekCompleted)
                            asyncResult.InvokeCallback();
                    }
                }
                else
                {
                    // Do internal processing in this handler to optimize context flowing.
                    lock (asyncResult.StartPostingAsyncOp())
                    {
                        SubmitRequest(true);
                        asyncResult.FinishPostingAsyncOp();
                    }
                    FinishRequestStage(RequestStage.CheckForError);
                }
            }
            catch (Exception exception)
            {
                if (NetEventSource.IsEnabled) NetEventSource.Error(this, exception);
                throw;
            }
            finally
            {
                if (NetEventSource.IsEnabled) NetEventSource.Exit(this);
            }

            return asyncResult;
        }