title: Reusing DataTemplates
body: <p>With a few <code>GroupBox</code>es in my UI, I'm modifying their <code>HeaderTemplate</code> to add icons in addition to the text caption. Here's my template:</p>
  
  <pre><code>&lt;DataTemplate&gt;
    &lt;Grid&gt;
      &lt;Grid.ColumnDefinitions&gt;
        &lt;ColumnDefinition Width="Auto" /&gt;
        &lt;ColumnDefinition Width="*" /&gt;
      &lt;/Grid.ColumnDefinitions&gt;
      &lt;Image Source="/Resources/IDCard.png" /&gt;
      &lt;TextBlock Grid.Column="1" Text="{Binding}" VerticalAlignment="Center" /&gt;
    &lt;/Grid&gt;
  &lt;/DataTemplate&gt;
  </code></pre>
  
  <p>This works, however since I have got multiple <code>GroupBox</code>es, I was thinking of a way to define this template in <code>Window</code>'s <code>Resources</code> and then reference it in each <code>GroupBox</code>. How can I use <code>ContentPresenter</code> (or anything else for that matter) in place of <code>&lt;Image&gt;</code> control in the above template and then provide the actual content (icon) in each <code>GroupBox</code> separately?</p>
  
  <p>Note: I'm looking for XAML-only solution.</p>