public void ClipViewChanged(object sender, NotifyCollectionChangedEventArgs e) { foreach (var it in ClipView.OfType<ClipViewModel>().Select((el, i) => new { Item = el, Index = i })) { if (it.Index < 10) { it.Item.IndexInClipView = it.Index; } else { it.Item.IndexInClipView = -1; } } }