Replacing TreeView with ListBox

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;

namespace MefBasic.Behaviors
{
    public class SelectionBehavior
    {
        public static DependencyProperty SelectionChangedProperty =
            DependencyProperty.RegisterAttached("SelectionChanged", typeof (ICommand), typeof (SelectionBehavior), new UIPropertyMetadata(OnPropertyChanged));

        public static void SetSelectionChanged(DependencyObject target, ICommand value)
        {
            target.SetValue(SelectionChangedProperty, value);
        }

        /// <exception cref="InvalidOperationException">This behavior can be attached to Selector item only.</exception>
        private static void OnPropertyChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            var element = target as Selector;
            if (element == null)
                throw new InvalidOperationException("This behavior can be attached to Selector item only.");
            if ((e.NewValue != null) && (e.OldValue == null))
            {
                element.SelectionChanged += SelectionChanged;
            }
            else if ((e.NewValue == null) && (e.OldValue != null))
            {
                element.SelectionChanged -= SelectionChanged;
            }
        }

        private static void SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            var element = (UIElement) sender;
            var command = (ICommand) element.GetValue(SelectionChangedProperty);
            command.Execute(((Selector) sender).SelectedValue);
        }
    }
}