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copied!<p>Typically you would enable intra-view communication using the <a href="http://www.dofactory.com/Patterns/PatternMediator.aspx" rel="nofollow">mediator pattern</a>, and not via a dependency property. This allows you to develop the views and controls independently of one another, as a mediator will provide loose coupling between the views.</p> <p>Assume you have 2 views, with View A containing Control A and View B containing Control B. You also have a view model for each view. The view model is where communication between views is going to occur by using a shared mediator. Alternately, you could add the mediator to each control as a dependency property and bind that property to the view model's mediator.</p> <p>View A</p> <ul> <li>Contains Control A</li> <li>Has its DataContext set to ViewModel A</li> <li>User interaction with Control A gets/sets view model properties using data binding</li> <li>View model contains a shared reference to the mediator/messenger</li> </ul> <p>View B</p> <ul> <li>Contains Control B</li> <li>Has its DataContext set to ViewModel B</li> <li>User interaction with Control B gets/sets view model properties using data binding</li> <li>View model contains a shared reference to the mediator/messenger</li> </ul> <p>So when a user interacts with control A on view A, the interaction causes the mediator to publish a message that contains information about the event. The view model of view B is subscribed to be notified when this message is published, and updates its properties, which triggers a change in control B via data binding.</p> <p>The mediator used by both view models is the same instance, often injected into the view models using an IoC container. Implementing a mediator is fairly trivial, and there are also several MVVM toolkits like MVVM Light that provide a 'Messenger' class that enables this sort of communication.</p> <p>The key idea is that your views and controls no longer have any knowledge of each other, and instead interaction is abstracted as the publication and subscription of messages; facilitating loosely coupled communication between different objects and object types.</p> <p>Mediator and MVVM resources:</p> <ol> <li><a href="http://marlongrech.wordpress.com/2009/04/16/mediator-v2-for-mvvm-wpf-and-silverlight-applications/" rel="nofollow">Simple Mediator</a></li> <li><a href="http://mvvmlight.codeplex.com/" rel="nofollow">MVVM Light Toolkit</a></li> <li><a href="http://msdn.microsoft.com/en-us/library/gg405484%28v=PandP.40%29.aspx" rel="nofollow">Implementing the MVVM Pattern</a></li> <li><a href="http://msdn.microsoft.com/en-us/library/ff921122%28v=PandP.40%29.aspx#sec8" rel="nofollow">Event Aggregation</a></li> </ol>

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