title: How to open a WPF Popup when another control is clicked, using XAML markup only?
body: <p>I've got two controls, a TextBlock and a PopUp. When the user clicks (MouseDown) on the textblock, I want to display the popup. I would think that I could do this with an EventTrigger on the Popup, but I can't use setters in an EventTrigger, I can only start storyboards. I want to do this strictly in XAML, because the two controls are in a template and I don't know how I'd find the popup in code.</p>
  
  <p>This is what conceptually I want to do, but can't because you can't put a setter in an EventTrigger (like you can with a DataTrigger):</p>
  
  <pre><code>&lt;TextBlock x:Name="CCD"&gt;Some text&lt;/TextBlock&gt;
  
  &lt;Popup&gt;
      &lt;Popup.Style&gt;
          &lt;Style&gt;
              &lt;Style.Triggers&gt;
                  &lt;EventTrigger SourceName="CCD" RoutedEvent="MouseDown"&gt;
                      &lt;Setter Property="Popup.IsOpen" Value="True" /&gt;
                  &lt;/EventTrigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/Popup.Style&gt;
  ...
  </code></pre>
  
  <p>What is the best way to show a popup strictly in XAML when an event happens on a different control?</p>