Question

I’m trying to use the async HttpWebRequest in Silverlight for Windows Phone. All works perfect until I get to the where I should call

private static ManualResetEvent allDone = new ManualResetEvent(false);
...
request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
allDone.WaitOne();
Debug.WriteLine("All done!");

In GetResponseCallback:

private void GetResponseCallback(IAsyncResult asynchronousResult)
{
    try
    {
        request = (HttpWebRequest)asynchronousResult.AsyncState;
        response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
        allDone.Set();
    }
    catch (Exception e)
    {
        Debug.WriteLine("Got Exception in GetResponseCallback: " + e.Message);
    }
}

After the call to allDone.WaitOne(); it just hangs…

Any suggestions on why?

Answer 1

This just takes a bit of a shift in thinking away from blocking/waiting to thinking in async terms on the WP7 platform. The result is the user is always able to interact with the UI.

Move a call to your completion code (writeline in this case) into your CompletedEventHandler and for any UI updates marshall back to the UI thread with

Dispatcher.BeginInvoke( () => { /* your UI update code */ } )

If there are any UI elements that should not be interacted with while your async op is executing then these controls can be hidden or disabled for the interim.