hi here's my question : well I want build a wp7 control,so I write it and all go well, but the problem is that I can intercept on write(see onItemsSourcePropertyChanged)but not on read I would like explain better: public static readonly DependencyProperty ItemsSourceProperty= DependencyProperty.Register( "ItemsSource", typeof(ObservableCollection<ObjWithDesc>), typeof(HorizontalListBox), new PropertyMetadata(OnItemsSourcePropertyChanged) ); static void OnItemsSourcePropertyChanged(DependencyObject obj,DependencyPropertyChangedEventArgs e) { ((HorizontalListBox) obj).OnItemsSourcePropertyChanged(e); } OnItemsSourcePropertyChanged is called when I use SetValue(dp,..) but there isn't onItemsSourcePropertyRead ? that is called when I Use GetValue()? thanks