how to pause the execution pointer using dispatcher in silverligh not wpf

We have the following problem: "blocking" or "modal" means that the instruction pointer of our execution should remain at its position as long as the dialog is shown, and when the dialog is closed, it should continue.
it is working in wpf

public bool ShowHandlerDialog(string message)
{
    Message = message;
    Visibility = Visibility.Visible;
    _parent.IsEnabled = false;
    _hideRequest = false;
    while (!_hideRequest)
    {
        // HACK: Stop the thread if the application is about to close
        if (this.Dispatcher.HasShutdownStarted || this.Dispatcher.HasShutdownFinished)
        {
            break;
        } // HACK: Simulate "DoEvents"
        this.Dispatcher.Invoke( DispatcherPriority.Background, new ThreadStart(delegate { }));
        Thread.Sleep(20);
    }
    return _result;
}

but same thing i want to implement in silverlight pls help me it's urgent