Getting the WebOperationContext of a HTTP response in Silverlight

20 October 2010

This came up as a question from a customer today: how do you get details of the HTTP response message that a WCF proxy in Silverlight received? If you thought of OperationContext and WebOperationContext, you’re on the right track, but you have only half of the story.

In Silverlight, in order to get to these context objects, you have to switch from the event-based async pattern to the more complex Begin/End-based async pattern. Within that pattern, you need to instantiate an OperationContextScope and call the End* method inside that scope, before you can access the context objects themselves. Check out this code snippet:

public MainPage()
{
    Service1 proxy = new Service1Client() as Service1;
    proxy.BeginDoWork(new AsyncCallback(Callback), proxy);
}

void Callback(IAsyncResult result)
{
    Service1 proxy = result.AsyncState as Service1;

    using(new OperationContextScope((proxy as Service1Client).InnerChannel))
    {
        string foo = proxy.EndDoWork(result);
        // Don't forget to reference System.ServiceModel.Web.Extensions.dll 
        // from the Silverlight SDK, otherwise WebOperationContext won't be
        // recognized

        // Get the HTTP status code or anything else WebOperationContext gives you
        HttpStatusCode status = WebOperationContext.Current.IncomingResponse.StatusCode;
    }
}

This is about as complex as WCF can ever get, so I thought I’d share :)