System.Windows.Controls.AutoCompleteBox.OnItemsSourceChanged C# (CSharp) Méthode

        private void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
        {
            // Remove handler for oldValue.CollectionChanged (if present)
            INotifyCollectionChanged oldValueINotifyCollectionChanged = oldValue as INotifyCollectionChanged;
            if(null != oldValueINotifyCollectionChanged && null != _collectionChangedWeakEventListener)
            {
                _collectionChangedWeakEventListener.Detach();
                _collectionChangedWeakEventListener = null;
            }

            // Add handler for newValue.CollectionChanged (if possible)
            INotifyCollectionChanged newValueINotifyCollectionChanged = newValue as INotifyCollectionChanged;
            if(null != newValueINotifyCollectionChanged)
            {
                _collectionChangedWeakEventListener = new WeakEventListener<AutoCompleteBox, object, NotifyCollectionChangedEventArgs>(this) { OnEventAction = (instance, source, eventArgs) => instance.ItemsSourceCollectionChanged(eventArgs), OnDetachAction = weakEventListener => newValueINotifyCollectionChanged.CollectionChanged -= weakEventListener.OnEvent };
                newValueINotifyCollectionChanged.CollectionChanged += _collectionChangedWeakEventListener.OnEvent;
            }

            // Store a local cached copy of the data
            _items = newValue == null ? null : new List<object>(newValue.Cast<object>().ToList());

            // Clear and set the view on the selection adapter
            ClearView();
            // ReSharper disable once PossibleUnintendedReferenceComparison
            if(SelectionAdapter != null && SelectionAdapter.ItemsSource != _view)
            {
                SelectionAdapter.ItemsSource = _view;
            }
            if(IsDropDownOpen)
            {
                RefreshView();
            }
        }