Resolving Download Failure in WebClient

Today I was developing a Silverlight client program which reads cross-domain content when I started facing Download Failure exception. This is code I was using, which resulted in exception

private void btnSearch_Click(object sender, RoutedEventArgs e){
string strTopic=txtSearchTopic.Text;
string strUrl = "";
            WebClient wc = new WebClient();
            wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler
(this.DownloadCompleted);
            wc.DownloadStringAsync(new Uri(strUrl));
        }
        private void DownloadCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            if (e.Error == null)
            {
                string strResult = e.Result;
            }
        }

So in this code, Line 10 was throwing Download failure exception probably because my domain in not registered in GroupPolicy.xml file on the server from which I was reading the content. Now the solution to this problem is to use System.Net.HttpWebRequest object which can easily read data across domains. So here are steps:

• Add Reference to System.Net assembly



• Add System.Net namespace and replace the previous code with this code

private void btnSearch_Click(object sender, RoutedEventArgs e)
        {
            string strTopic = txtSearchTopic.Text;
              string strUrl = "";
              HttpWebRequest objRq = (HttpWebRequest)WebRequest.Create(new Uri(strUrl));
         
              objRq.BeginGetResponse(new AsyncCallback(responseHandler), objRq);       
         
        }
        void responseHandler(IAsyncResult asyncResult)
        {
            HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
            HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);
            Stream respStream = response.GetResponseStream();
            if (respStream != null)
            {
                StreamReader sr = new StreamReader(respStream);
  //Here you will get the content in strResp string
                string strResp = sr.ReadToEnd();
               
            }         
        }

And the above code worked.

Technorati Tags: Download Failure,Download Failure Silverlight,Download Failure Webclient,webclient silverlight,silverlight cross domain

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