title: How to get the "{Binding}" instance from within the behavior?
body: <p>I created a behavior to validate a control whenever there's an <strong>error</strong>. The behavior needs to know the <code>Binding</code> (viewmodel) source of the control because the <code>ViewModel</code> implements <code>IDataErrorInfo</code> and the behavior needs to subscribe to <code>the ErrorChanged</code> event to make the appropriate action when an error occurs. </p>
  
  <p>To do that, I added a dependency property ValidationSource which will always be set to <code>"{Binding}"</code>.</p>
  
  <pre><code>&lt;TextBox Text="{Binding LastName, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"&gt;
    &lt;i:Interaction.Behaviors&gt;
      &lt;b:MyValidateOnErrorBehavior PropertyName="LastName" ValidationSource="{Binding}" /&gt;
    &lt;/i:Interaction.Behaviors&gt;
  &lt;/TextBox&gt;
  </code></pre>
  
  <p>This solution works for me but I don't want to type <code>ValidationSource="{Binding}"</code> all the time. </p>
  
  <p>Is there a way from within the behavior to get to the <code>"{Binding}"</code> instance without having to set it in the dependency property? </p>