Silverlight: ListBox ItemsChanged event

Bits me why this is not implemented.
i was missing an event on the ListBox – ItemsChanged.
as you can see the implementation is so easy:

using System.Collections.Specialized;
...
public class ListBoxGeneric : ListBox
{
    #region Constructor
    public ListBoxGeneric() : base() { }
    #endregion  Constructor

    #region Override
    protected override void OnItemsChanged(
        NotifyCollectionChangedEventArgs e)
    {
        base.OnItemsChanged(e);
        OnItemsChangedEvent(e);
    }
    #endregion Override

    #region Class Events

    public delegate void ItemsChangedEventHandler(object sender,
        NotifyCollectionChangedEventArgs e);
    public event ItemsChangedEventHandler ItemsChanged;

    private void OnItemsChangedEvent(
        NotifyCollectionChangedEventArgs e)
    {
        if (ItemsChanged != null)
        {
            ItemsChanged(this, e);
        }
    }

    #endregion Class Events
}