title: HttpWebRequest.EndGetResponse throws a NotSupportedException in Windows Phone 7
body: <p>in a Silverlight-Windows Phone 7-project I am creating an HttpWebRequest, get the RequestStream, write something into the Stream and try to get the response, but I always get a NotSupportedException: 
  "System.Net.Browser.OHWRAsyncResult.AsyncWaitHandle threw an exception of type 'System.NotSupportedException'</p>
  
  <p>My production code is far more complicated, but I can narrow it down to this small piece of code:</p>
  
  <pre><code>public class HttpUploadHelper
  {
      private HttpWebRequest request;
      private RequestState state = new RequestState();
  
      public HttpUploadHelper(string url)
      {
          this.request = WebRequest.Create(url) as HttpWebRequest;
          state.Request = request;
      }
  
      public void Execute()
      {
          request.Method = "POST";
          this.request.BeginGetRequestStream(
              new AsyncCallback(BeginRequest), state);
      }
  
      private void BeginRequest(IAsyncResult ar)
      {
          Stream stream = state.Request.EndGetRequestStream(ar);
          state.Request.BeginGetResponse(
              new AsyncCallback(BeginResponse), state);
      }
  
      private void BeginResponse(IAsyncResult ar)
      {
          // BOOM: NotSupportedException was unhandled; 
          // {System.Net.Browser.OHWRAsyncResult}
          // AsyncWaitHandle = 'ar.AsyncWaitHandle' threw an 
          // exception of type 'System.NotSupportedException'
          HttpWebResponse response = state.Request.EndGetResponse(ar) as HttpWebResponse;
          Debug.WriteLine(response.StatusCode);
      }
  }
  
  public class RequestState
  {
      public WebRequest Request;
  }
  </code></pre>
  
  <p>}</p>
  
  <p>Does anybody know what is wrong with this code?</p>