Provides types and interfaces that allow the creation of observable types that provide notifications to clients when changes are made to it. Commonly Used Types: System.ComponentModel.INotifyPropertyChanged System.Collections.ObjectModel.ObservableCollection<T> System.ComponentModel.PropertyChangedEventHandler System.Windows.Input.ICommand System.Collections.Specialized.INotifyCollectionChanged System.Collections.Specialized.NotifyCollectionChangedEventArgs System.Collections.Specialized.NotifyCollectionChangedEventHandler System.Collections.ObjectModel.KeyedCollection<TKey, TItem> System.ComponentModel.PropertyChangedEventArgs System.Collections.ObjectModel.ReadOnlyDictionary<TKey, TValue> When using NuGet 3.x this package requires at least version 3.4.