protected override void OnStartDemo(IViewport viewport)
        {
            IUIRootElement root         = viewport.Root;
            IUIBoxElement  sampleButton = (IUIBoxElement)root.CreateElement2(BasicUIElementKind.SimpleBox);

            root.AddContent(sampleButton);
            sampleButton.SetLocation(20, 20);

            IUIBoxElement textbox = (IUIBoxElement)root.CreateElement2(BasicUIElementKind.TextBox);

            root.AddContent(textbox);
            textbox.SetLocation(20, 60);
            textbox.SetSize(100, 24);

            IUIEventListener evListener = root.CreateEventListener();
            int count = 0;

            evListener.MouseDown += (e) =>
            {
                System.Console.WriteLine("click :" + (count++));
            };


            sampleButton.AttachEventListener(evListener);
        }