RadListBox EmptyDataTemplate Behavior

[David]

Attempting to create a behavior for the Silverlight RadListBox which implements the EmptyDataTemplate seen in the ASP.NET RadListBox. So far, I have the behavior created and declared in XAML, but one problem is that RadListBox.Items does not have a CollectionChanged event. So, I decided to use the SelectionChanged in order to asynchronously detect changes to the ListBox. Not the best choice, but just testing the waters.

Here is the behavior implementation:

public class EmptyListBoxBehavior : Behavior<RadListBox>
{
    public DataTemplate EmptyDataTemplate { get; set; }
    private ContentPresenter contentPresenter = new ContentPresenter();

    protected override void OnAttached()
    {
        base.OnAttached();

        LoadEmptyDataTemplate();
        this.AssociatedObject.LayoutUpdated += AssociatedObject_LayoutUpdated;
    }

    private void AssociatedObject_LayoutUpdated(object sender, EventArgs e)
    {
        this.AssociatedObject.LayoutUpdated -= AssociatedObject_LayoutUpdated;

        this.AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged; // HACK RadListBox.Items.CollectionChanged does not exist
        SetEmptyDataTemplateVisibility();
    }

    void AssociatedObject_SelectionChanged(object sender, Telerik.Windows.Controls.SelectionChangedEventArgs e)
    {
        SetEmptyDataTemplateVisibility();
    }

    private void LoadEmptyDataTemplate()
    {
        contentPresenter.IsHitTestVisible = false;
        contentPresenter.DataContext = this;
        contentPresenter.ContentTemplate = this.EmptyDataTemplate;

        // Need to find which type of child is needed here (must inherit from DependencyObject)
        var child = this.AssociatedObject.ChildrenOfType<DependencyObject>().ToList();

        // TODO Not sure where to add the DataTemplate?
        // In RadGridView, you can do: RadGridView.ChildrenOfType<Grid>().First() and add it there by,
        // Grid.Children.Add(contentPresenter)
    }

    private void SetEmptyDataTemplateVisibility()
    {
        contentPresenter.Visibility = this.AssociatedObject.Items.Count == 0
            ? Visibility.Visible
            : Visibility.Collapsed;
    }
}

The last piece here is determining how/where to add the ContentPresenter to the visual elements of the RadListBox.

[Vladi]

Hello,

In the RadListBox control for Silverlight there isn't a CollectionChanged on its items. If you have bound the ItemsSource property of the control to a ObservableCollection you could use its CollectionChanged instead. In order to edit the template of the items you should create a custom Template and set it to the ItemTemplate of the ListBox control.

Hope this is helpful.

Regards,
Vladi
Telerik