It works because an ICollectionView has the CurrentItem property and all collections have a default view instance that can be accessed by calling GetDefaultView(). So, when you bind a regular collection, such as an ObservableCollection, then WPF automatically binds to its default view (see Using a default View).

It works because an ICollectionView has the CurrentItem property. All collections have a default view instance that you can access by calling GetDefaultView(). So, when you bind a regular collection, such as an ObservableCollection, then WPF automatically uses its default view (see Using a default View).