title: Can't assign RoutedEvent to Binding.TargetUpdated
body: <p>I have a textblock which should react for changing its text (it must display text for few seconds, and then dissapear).</p>
  
  <pre><code> &lt;TextBlock Text="{Binding Path=OperationMessage, NotifyOnValidationError=True}" x:Name="label_OperationMessage" Visibility="Collapsed" HorizontalAlignment="Right" Margin="3,3,3,3" &gt;
                   &lt;TextBlock.Triggers&gt;
  &lt;EventTrigger RoutedEvent="Binding.TargetUpdated"&gt;
  &lt;BeginStoryboard&gt;
  &lt;Storyboard&gt;
  &lt;DoubleAnimation Storyboard.TargetProperty="Opacity" Duration="0:0:0" To="1.0" /&gt;
  &lt;DoubleAnimation Storyboard.TargetProperty="Opacity" Duration="0:0:2" From="1.0" To="0.0" BeginTime="0:0:5" /&gt;
  &lt;/Storyboard&gt;
  &lt;/BeginStoryboard&gt;
  &lt;/EventTrigger&gt;
  &lt;/TextBlock.Triggers&gt;
              &lt;/TextBlock&gt;
  </code></pre>
  
  <p>When I launch my app I get error :</p>
  
  <pre><code>Failed to assign to property 'System.Windows.EventTrigger.RoutedEvent'. 
  </code></pre>
  
  <p>on the line</p>
  
  <pre><code>&lt;EventTrigger RoutedEvent="Binding.TargetUpdated"&gt;
  </code></pre>
  
  <p>What is wrong with this code?</p>