Data-Driven Services with Silverlight 2

Lists and Notifications

Entities can implement the INotifyPropertyChanged interface to communicate with the target controls to notify them when a property value has changed. Lists of items can also receive notifications when the contents of the list have changed. The ObservableCollection<T> is a special collection that works well with XAML-based bindings to notify binding targets when a change has been made to a list of items in the ObservableCollection<T>.

ObservableCollection<T>

The ObservableCollection<T>, part of the System.Collections.ObjectModel namespace, implements both the INotifyPropertyChanged and INotifyCollectionChanged interfaces. When a class inherits from the ObservableCollection<T>, the derived class also gets the benefit of the INotifyPropertyChanged interface. This allows the derived class to raise the PropertyChanged event for the ObservableCollection<T>-derived class when a property on the collection has changed.

Note

Although this section of the chapter focuses on using the ObservableCollection<T> for list-based binding and notifications, any collection class that implements the INotifyCollectionChanged interface will also reap the benefits discussed here.

Notice that in Figure 4-5, where the members of ObservableCollection<T> are displayed, the PropertyChanged event is listed as a protected event, which allows classes that inherit from ObservableCollection<T> to implement the event. In fact, most of the members of the ObservableCollection<T> collection are protected, ...