title: How do I create a fade-out transition with a WPF border on mouse hover?
body: <p>I am trying to create a <code>Border</code> that shows/hides the border itself on hover.  The desired effect is to show a border around content on hover and when the mouse leaves the area, the border fades out.  I can't figure out the "fading out" part.  </p>
  
  <p>The snippet below uses style <code>Trigger</code>s.  It works as far as toggling the border color.  How can I achieve the fade-out?</p>
  
  <pre><code>&lt;Border
      BorderThickness="1"
      &gt;
      &lt;Border.Style&gt;
          &lt;Style&gt;
              &lt;Style.Triggers&gt;
                  &lt;Trigger
                      Property="Border.IsMouseOver"
                      Value="false"&gt;
                      &lt;Setter
                          Property="Border.BorderBrush"
                          Value="Transparent" /&gt;
                  &lt;/Trigger&gt;
                  &lt;Trigger
                      Property="Border.IsMouseOver"
                      Value="true"&gt;
                      &lt;Setter
                          Property="Border.BorderBrush"
                          Value="LightGray" /&gt;
                  &lt;/Trigger&gt;
              &lt;/Style.Triggers&gt;
          &lt;/Style&gt;
      &lt;/Border.Style&gt;
  </code></pre>