UI update in WPF elements event handlers

There is a problem with UI update in WPF.

I have such code:

    private void ButtonClick_EventHandler(object sender, RoutedEventArgs e)
    {
        Label.Visibility = Visibility.Visible;
        TextBox.Text = "Processing...";

        LongTimeMethod(); //some long operation
    }

The problem is that until LongTimeMethod ends (that is event handler ends), Label.Visibility and TextBox.Text will not be changed.

I solved it like this so far:

    private void ButtonClick_EventHandler(object sender, RoutedEventArgs e)
    {
        Label.Visibility = Visibility.Visible;
        TextBox.Text = "Processing...";

        Dispatcher.BeginInvoke(new Action(LongTimeMethod), 
            DispatcherPriority.Background);
    }

Is there any other solution without using dispatcher invocation? Calling this.UpdateLayout() doesn't help.