Question

I defined an attached dependency property of collection type:

var selSrcPropMetadata = new PropertyMetadata(SelectionSourceChanged);
SelectionSourceProperty = DependencyProperty.RegisterAttached("SelectionSource",
                                                        typeof(IEnumerable), 
                                                        typeof(SelectionHelper), 
                                                        selSrcPropMetadata);

Property change callback works only once when binding is applied.
But how can I get the notifications about bound collection changes?

Answer 1

In SelectionSourceChanged, check if the new source value implements INotifyCollectionChanged. If it does, cast it and subscribe to its CollectionChanged event.