title: How to set a value in a ViewModel from binding?
body: <p>Kind of an odd question- if I'm thinking of this the wrong way please let me know.  I am using an infragistics dock manager, which manages tabs as well.  So I can create a <code>TabGroupPane</code>, and then add multiple <code>ContentPanes</code>, each of which has its own tab.</p>
  
  <p>In each content pane, I set my viewmodel:</p>
  
  <pre><code>&lt;ContentPane&gt;
    &lt;viewmodels:MyViewModelForTab1 /&gt;
  &lt;/ContentPane&gt;
  </code></pre>
  
  <p>So here's the problem- while using a mediator pattern for communication, my viewmodels have no idea if they are on the visible tab or not, so they are always working even if hidden.  The <code>TabGroupPane</code> does have a <code>SelectedTab</code> property, as well as each <code>ContentPane</code> having an <code>IsActive</code> property.  </p>
  
  <p>So the question is how do I set that information in my ViewModel?  Making my VM a dependency object seems like a bad idea since I already implement <code>INotifyPropertyChanged</code>.  Using a CLR prop in my VM also doesnt work, since you cannot bind to it.</p>
  
  <p>How can I get my VM to know if it is the datacontext of an active tab?</p>
  
  <p>Thanks!</p>