How to dismiss a popup in Silverlight when clicking outside of the control?

Question

In my Silverlight UI, I have a button that when clicked pops up a control with some filtering parameters. I would like this control to hide itself when you click outside of it. In other words, it should function in a manner similar to a combo box, but it's not a combo box (you don't select an item in it). Here's how I'm trying to capture a click outside of the control to dismiss it:

public partial class MyPanel : UserControl
{
    public MyPanel()
    {
        InitializeComponent();
    }

    private void FilterButton_Click(object sender, RoutedEventArgs e)
    {
        // Toggle the open state of the filter popup
        FilterPopup.IsOpen = !FilterPopup.IsOpen;
    }

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        // Capture all clicks and close the popup
        App.Current.RootVisual.MouseLeftButtonDown += delegate {
            FilterPopup.IsOpen = false; };
    }
}

Unfortunately, the event handler for MouseLeftButtonDown is never getting fired. Is there a well-established way of making a popup control that auto-dismisses when you click outside of it? If not, why isn't my MouseLeftButtonDown handler firing?

Solution:

I thought I'd post my entire solution in case others find it helpful. In my top-level visual, I declare a "shield" for the popups, like this:

<UserControl xmlns:my="clr-namespace:Namespace"
    x:Class="Namespace.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation" 
    xmlns:uriMapper="clr-namespace:System.Windows.Navigation;assembly=System.Windows.Controls.Navigation"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
>
  <Grid Background="Black" HorizontalAlignment="Stretch" 
          VerticalAlignment="Stretch">
    <my:MyStuff/>
    <Canvas HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
            x:Name="PopupShield" Background="Transparent" Width="Auto" 
            Height="Auto" Visibility="Collapsed"/>
  </Grid>
</UserControl>

Then, I added an extension method for the Popup class, like this:

public static class PopupUtils
{
    public static void MakeAutoDismissing(this Popup popup)
    {
        var shield = (App.Current.RootVisual as MainPage).PopupShield;

        // Whenever the popup opens, deploy the shield
        popup.HandlePropertyChanges(
            "IsOpen",
            (s, e) =>
            {
                shield.Visibility = (bool)e.NewValue 
                    ? Visibility.Visible : Visibility.Collapsed;
            }
        );

        // Whenever the shield is clicked, dismiss the popup
        shield.MouseLeftButtonDown += (s, e) => popup.IsOpen = false;
    }
}

public static class FrameworkUtils
{
    public static void HandlePropertyChanges(
        this FrameworkElement element, string propertyName, 
        PropertyChangedCallback callback)
    {
        //Bind to a depedency property
        Binding b = new Binding(propertyName) { Source = element };
        var prop = System.Windows.DependencyProperty.RegisterAttached(
            "ListenAttached" + propertyName,
            typeof(object),
            typeof(UserControl),
            new System.Windows.PropertyMetadata(callback));

        element.SetBinding(prop, b);
    }
}

The extension method is used like this:

private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
    FilterPopup.MakeAutoDismissing();
}

Answer 1

Did you set a background color on your RootVisual?