NotifyObservableCollection.OnCollectionChanged C# (CSharp) Méthode

        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (e.NewItems != null) {
                foreach (object t in e.NewItems) {
                    ((T) t).PropertyChanged += Handle;
                }
            }
            if (e.OldItems != null) {
                foreach (object t in e.OldItems) {
                    ((T) t).PropertyChanged -= Handle;
                }
            }
            base.OnCollectionChanged(e);
        }