title: Down state in a toolbar button group
body: <p>Consider the following xaml snippet:</p>
  
  <pre><code>    &lt;ToolBarTray&gt;
          &lt;ToolBar Band="1" BandIndex="1"&gt;
              &lt;Button&gt;Go&lt;/Button&gt;
              &lt;Separator&gt;&lt;/Separator&gt;
              &lt;Button&gt;Camera 1&lt;/Button&gt;
              &lt;Button&gt;Camera 2&lt;/Button&gt;
              &lt;Button&gt;Camera 3&lt;/Button&gt;
          &lt;/ToolBar&gt;
  
      &lt;/ToolBarTray&gt;
  </code></pre>
  
  <p>How can I set the Camera 1 - 3 in a way that when one of them is clicked it stays down (selected)?</p>