WPF Concepts: Implict ZIndex, Explicit ZIndex & Popup

I’m going over some API feedback/questions here.

To help illustrate ZIndex & Popup, I wrote a quick sample to illustrate the differences between:
1) implicit zindex based on tree order (green will be on top of red due to this)
2) explicit zindex (any element can pop out of implicit zindex order with Panel.ZIndex)
3) using <Popup /> (popups appear above all elements and can go outside the window)

You can download the sample from http://robrelyea.com/demos/ZIndexPopupExample/ZIndex.zip (this project was created in VS "Orcas" Beta1 targetting .Net 3.0.)

Window1.xaml:

<Window x:Class="ZIndexPopupExample.Window1"
   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation&quot;
   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml&quot;
   Title="ZIndex-Implicit by order in tree vs Explicit" Height="300" Width="800"
   PreviewKeyDown="handleKeyDown"
   >
   <Grid>
       <Canvas Margin="10,10,10,100" Background="Blue" Visibility="Hidden" Name="explicitZIndex" Panel.ZIndex="1" />
       <Label IsTabStop="True" Name="Instructions" VerticalAlignment="Bottom" HorizontalAlignment="Center" MinWidth="1in" xml:space="preserve">‘B’, ‘R’, ‘P’ – Show/Hide Blue Rect, Red Rect, or Popup.
‘Esc’ to reset All.</Label>
       <Canvas Margin="10,10,100,50" Background="Red" Visibility="Hidden" Name="implicitZIndex" />
       <Canvas Height="10" Width="10" Background="Green" VerticalAlignment="Center" HorizontalAlignment="Center" />
       <Popup Name="popup" PopupAnimation="Fade" Placement="Center" Width="1200"><TextBlock Padding="30" Background="Orange">I’m a popup</TextBlock></Popup>
   </Grid>
</Window>

Window1.xaml.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Shapes;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;

namespace ZIndexPopupExample
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>

    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            Instructions.Focus();
        }

        void handleKeyDown(object sender, KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.B:
                    ToggleVisibility(explicitZIndex);
                    break;
                case Key.R:
                    ToggleVisibility(implicitZIndex);
                    break;
                case Key.P:
                    popup.IsOpen = !popup.IsOpen;
                    break;
                case Key.Escape:
                    explicitZIndex.Visibility = Visibility.Hidden;
                    implicitZIndex.Visibility = Visibility.Hidden;
                    popup.IsOpen = false;
                    break;
            }
        }

        void ToggleVisibility(UIElement element)
        {
            switch (element.Visibility)
            {
                case Visibility.Collapsed: //just put this one in for completeness…
                    element.Visibility = Visibility.Visible;
                    break;
                case Visibility.Hidden:
                    element.Visibility = Visibility.Visible;
                    break;
                case Visibility.Visible:
                    element.Visibility = Visibility.Hidden;
                    break;

            }
        }
    }
}