title: The property 'Content' is set more than once when I add Style
body: <p>When I use this:</p>
  
  <pre><code>&lt;Label Grid.Column="2"
         Grid.Row="8" 
         Content="{x:Static res:Strings.ToolPanelEditView_Validation_MandatoryField}" &gt;
  &lt;/Label&gt;
  </code></pre>
  
  <p>It runs just fine.</p>
  
  <p>But when I add the Style tag:</p>
  
  <pre><code> &lt;Label Grid.Column="2"
          Grid.Row="8" 
          Content="{x:Static res:Strings.ToolPanelEditView_Validation_MandatoryField}" &gt;
      &lt;Style&gt;
          &lt;Setter Property="Label.Margin" Value="0" /&gt;
      &lt;/Style&gt;
  &lt;/Label&gt;
  </code></pre>
  
  <p>It doesn't compile saying:</p>
  
  <blockquote>
    <p>The property 'Content' is set more than once</p>
  </blockquote>