Wandering through the Wilderness - Creating popup windows in XBAP applications

Thursday, April 03, 2008

Creating popup windows in XBAP applications

A colleague at DevelopMentor recently asked me about creating popup windows in XAML browser applications (XBAP). Normally this is not allowed - if you try to create a top-level window you will get a SecurityException because WPF asks for UIPermission which is strictly prohibited when hosted in the browser. It turns out, however, that you can get a popup window - there's a hidden little gem in the System.Windows.Controls.Primitive namespace that is your friend: Popup. It's the same underlying class that ToolTip, Menu, and ComboBox use to display drop-down menus and overlays and it is browser-hosting aware! It's pretty limited in functionality - I'm not sure you can get it to move around with the mouse for example, but for simple cases it works great. Here's a code snippet - wire this up to a button in an XBAP:

   1: void OnClick(object sender, EventArgs e)

   2: {

   3:    Popup window = new Popup();

4:

   5:    StackPanel sp = new StackPanel { Margin = new Thickness(5) };

   6:    sp.Children.Add(new TextBlock { Text = "Hi from a popup" });

   7:    Button newButton = new Button { Content = "Another button" };

   8:    newButton.Click += delegate { window.IsOpen = false; };

   9:    sp.Children.Add(newButton);

  10:    sp.Children.Add(new Slider { Minimum = 0, Maximum = 50, Value = 25, Width = 100 });

11:

  12:    window.Child = new Border { Background = Brushes.White, BorderBrush = Brushes.Black, 
                                     BorderThickness = new Thickness(2), Child = sp };

  13:    window.PlacementTarget = this;

  14:    window.Placement = PlacementMode.Center;

15:

  16:    window.IsOpen = true;

  17: }

The key thing you need to do is set the PlacementTarget. That associates a "parent" window and without it, the Popup class asserts UIPermission which will fail in the browser environment.

Thursday, April 03, 2008 9:47:05 AM (Central Daylight Time, UTC-05:00)

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