Sample.cs

protected static void OnMyCollectionItemsSourceChanged(DependencyObject property, DependencyPropertyChangedEventArgs args)
{
    var newCol = args.NewValue as INotifyCollectionChanged;
    if (newCol != null)
    {
        // CollectionChangedEventManager.AddListener(newCol, this); // You probably wanna do this in a control
        newCol.CollectionChanged += OnCollectionChanged;
    }
    var oldCol = args.OldValue as INotifyCollectionChanged;
    if (oldCol != null)
    {
        //CollectionChangedEventManager.RemoveListener(oldCol, this); //
        oldCol.CollectionChanged -= OnCollectionChanged;
    }
}
private static void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs notifyCollectionChangedEventArgs)
{
    System.Diagnostics.Debug.WriteLine("MyCollection Updated");
}