A simple class to manage dispatching calls to a UI thread in a silverlight application (might work in WPF too, I haven't tried it!)

    public static class UIThread
    {
        private static readonly Dispatcher Dispatcher;

        static UIThread()
        {
            Dispatcher = Deployment.Current.Dispatcher;
        }

        public static void Invoke(Action action)
        {
            if (Dispatcher.CheckAccess())
                action();
            else
                Dispatcher.BeginInvoke(action);
        }
    }