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copied!<p>The reason that there is no ObservableKeyedCollection (or any other such type which is merely a combination of other generic types) is because <a href="http://msdn.microsoft.com/en-us/library/ms668604.aspx" rel="nofollow noreferrer">ObservableCollection</a> is generic, and that makes implementation of an "ObservableKeyedCollection" as easy as this:</p> <pre><code>using System; using System.Collections.Generic; using System.Collections.ObjectModel; using System.Collections.Specialized; public class DictionaryWatcher : ObservableCollection<KeyValuePair<string, object>>, IDisposable { private NotifyCollectionChangedEventHandler watcher; private bool watching = false; public DictionaryWatcher() { watcher = new NotifyCollectionChangedEventHandler( ReportChange ); CollectionChanged += watcher; Watched = true; } public bool Watched { get { return watching; } set { if (watching) { lock (this) { CollectionChanged -= watcher; watching = false; } } } } public void Dispose() { Dispose( true ); GC.SuppressFinalize( this ); } public void Initialize() { this.Add( new KeyValuePair<string, object>( "First", 1 ) ); this.Add( new KeyValuePair<string, object>( "Second", 2 ) ); this.Add( new KeyValuePair<string, object>( "Turd", 3 ) ); KeyValuePair<string, object> badValue = this[2]; this.Remove( badValue ); } protected virtual void Dispose( bool disposing ) { if (disposing && Watched) { Watched = false; } } private void ReportChange( object sender, NotifyCollectionChangedEventArgs e ) { Console.WriteLine( "Change made: {0}", e.Action ); } } </code></pre> <p>While that is certainly not a one-liner program, most of it is boilerplate. Most importantly, it doesn't re-implement the <a href="http://msdn.microsoft.com/en-us/library/ms668604.aspx" rel="nofollow noreferrer">ObservableCollection</a> as you were suggesting; instead it fully utilizes it.</p> <p>The reason that it "whouldn't be a good addition to the .NET Framework" is because when there's already one way to do something, creating another way to do it is a bad idea. The fewer ways there are to get some particular task done, the fewer ways there are to do it poorly. 8 )</p> <p>The tools are provided, it's now all about how you use them.</p> <p>Hope that helps!</p>

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