异步HttpWebRequest捕获WebException

Question

我正在尝试从异步WebException捕获HttpWebRequest以从HttpWebRequest读取soap:fault。但它抛出了AggregateException。有什么方法可以捕获异步WebException吗？

public async Task<XDocument> GetXmlSoapResponseAsync(string soapRequestURL, string xmlData)
    {
      try
      {
        //create xml doc
        XmlDocument doc = new XmlDocument();

        //load xml document frtom xmlData
        doc.LoadXml(xmlData);
        //creta web request
        HttpWebRequest req = (HttpWebRequest)WebRequest.Create(soapRequestURL);
        req.ContentType = "text/xml";
        req.Accept = "text/xml";
        req.Method = "POST";

        //GetRequestStream from req
        Stream stm = req.GetRequestStream();
        doc.Save(stm);
        stm.Close();

        Task<WebResponse> task = Task.Factory.FromAsync(
        req.BeginGetResponse,
        asyncResult => req.EndGetResponse(asyncResult),
        (object)null);

        var response = task.Result;
        return await task.ContinueWith(t => ReadStreamFromResponse(response,stm, soapRequestURL,xmlData));
      }
      catch (WebException webException)
      {
        LogWebException(webException, soapRequestURL, xmlData);

        return null;
      }

    }

Answer 1

改变这个

var response = task.Result;

到这个

var response = await task;

await返回任务的结果或打开AggregateException (如果有的话)。

另外，.Result会阻塞当前线程，直到结果可用为止，这可能不是您想要的，否则您只需要使用阻塞GetResponse，而不是异步BeginGetResponse和EndGetResponse。

而且，你甚至不需要这两种方法。还有一个更好的-- GetResponseAsync

用这个：

var response = await req.GetResponseAsync();

而不是这样：

Task<WebResponse> task = Task.Factory.FromAsync(
req.BeginGetResponse,
asyncResult => req.EndGetResponse(asyncResult),
(object)null);

var response = task.Result;