Invoking UI thread from BeginGetResponse in Silverlight

I know how to do this in everyday .NET, but mucking rou开发者_StackOverflownd with WP7 development and Silverlight is driving me mad. An HttpWebRequest response must be done async, cool with that, but how can I invoke the UI thread from the async method?

i.e.

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create('http://stackoverflow.com');
request.BeginGetResponse(new AsyncCallback(onRequestComplete), request);

I'm calling this in a class, which has a delegate set up. I'd like to call the delegate on the UI thread from onRequestComplete. I know I can do this the other way round, invoke from the delegate, but I feel this would be cleaner.

Thanks in advance

You need to have access to the relevant Dispatcher, and then call Dispatcher.BeginInvoke.

Any UI elements will have access to the system dispatcher via the Dispatcher property. If you need to do this in a testable way, you may want to abstract out the dispatcher into an IDispatcher interface with an implementation to use the normal one for production, and something like a SameThreadDispatcher in tests.