I'm trying to add some dynamic controls to my Silverlight page after a WCF call. When I try to add a control to I get an error: Object reference not set to an instance of an object.

Here is a simplified version of my code:

using edm = SilverlightBusinessApplication.ServiceRefrence;

public partial class ListWCF : Page
    {
        edm.ServiceClient EdmClient = new ServiceClient();
        public ListWCF()
        {
            EdmClient.GetTestCompleted += EdmGetTestCompleted;
            EdmClient.GetTestAsync();
        }

        private void EdmGetTestCompleted(object sender, edm.GetTestCompletedEventArgs e)
        {
            //This is where I want to add my controls
            Button b = new Button();
            LayoutRoot.Children.Add(b); //Error: Object reference not set to an instance of an object
        }

    }

Is it not possible to modify the page after it has been loaded? What am I missing?

Thanks