title: Set GroupStyle inside style on xaml
body: <p>I'm Trying to set default style for ContexMenu and I want to set default GroupStyle to ContexMenu inside the style. Something like this:</p>
  
  <pre><code>&lt;Setter Property="ItemsControl.GroupStyle"&gt;
      &lt;Setter.Value&gt;
         &lt;GroupStyle&gt;
            &lt;...&gt;
          &lt;/GroupStyle&gt;
      &lt;/Setter.Value&gt;
  &lt;/Setter&gt;
  </code></pre>
  
  <p>But the compiler say error: it can't find GroupStyle on ItemsControl.</p>
  
  <p>However ,in code I can do simply:</p>
  
  <pre><code>ContextMenu contextMenu;
  contextMenu.GroupStyle.Add(someSavedStyle);
  </code></pre>
  
  <p>How can I achieve this in xaml?</p>
  
  <p>Thanks in advance! </p>