title: Caliburn.Micro Action doesn't work
body: <p>I have a WPF application with Caliburn.Micro.</p>
  
  <p>I want to handle slider's move, i.e. MouseUp event.</p>
  
  <pre><code>&lt;Slider cal:Message.Attach="[Event MouseUp] = [Action OnSliderMouseUp($this)]"  
          Value="{Binding  PlayerPosition, Mode=OneWay}" MinWidth="200" 
          VerticalAlignment="Center" Minimum="0" 
          Maximum="{Binding Player.NaturalDuration.TimeSpan.TotalMilliseconds}"/&gt;
  </code></pre>
  
  <p>In ViewModel:</p>
  
  <pre><code>public void OnSliderMouseUp(Slider slider)
  {
      int blah = 9;
  }
  </code></pre>
  
  <p><code>OnSliderMouseUp()</code> is never called. Could you please tell what I am missing? </p>