异步回调.Net中的异常处理

Question

我正在制作异步请求BeginGetRequestStream，其中回调处理EndRequest。我想将回调方法ReadCallback()中发生的任何异常发送回主调用方法InsertSoapEnvelopeIntoWebRequest。

private void InsertSoapEnvelopeIntoWebRequest(XmlDocument soapEnvelopeXml,        
HttpWebRequest webRequest)
{
      try
      {
        webRequest.ContentLength = soapEnvelopeXml.InnerXml.Length;
        this.soapEnvelopeXml = soapEnvelopeXml;
        allDone = new ManualResetEvent(false);
        IAsyncResult r = (IAsyncResult)webRequest.BeginGetRequestStream(
           new AsyncCallback(ReadCallback), webRequest);
        allDone.WaitOne();         
       }
       catch(Exception ex)
       {
         throw;
       }
    }




private void ReadCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest myRequestState = (HttpWebRequest)asynchronousResult.AsyncState;   
        byte[] byteArray = null;   
        using (Stream streamResponse =                                 
                             myRequestState.EndGetRequestStream(asynchronousResult))
        {             
            byteArray = Encoding.UTF8.GetBytes(soapEnvelopeXml.InnerXml);
            streamResponse.Write(byteArray, 0, byteArray.Length);             
        }
        allDone.Set();
    }

我如何实现这一目标？

谢谢， GAGAN