title: WPF Combobox Validation.ErrorTemplate error
body: <p>I have a combobox that i need to edit its error template to show a red border when there is a validation error.</p>
  
  <p>I am using the following style</p>
  
  <pre><code>&lt;Style TargetType="{x:Type ComboBox}" &gt;
      &lt;Setter Property="Validation.ErrorTemplate"&gt;
          &lt;Setter.Value&gt;
              &lt;ControlTemplate&gt;
                  &lt;DockPanel&gt;
                      &lt;Border BorderBrush="Red" BorderThickness="3"&gt;
                          &lt;AdornedElementPlaceholder /&gt;
                      &lt;/Border&gt;
                  &lt;/DockPanel&gt;
              &lt;/ControlTemplate&gt;
          &lt;/Setter.Value&gt;
      &lt;/Setter&gt;
      &lt;Setter Property="FontFamily" Value="Segoe UI" /&gt;
      &lt;Setter Property="FontSize" Value="12" /&gt;
      &lt;Setter Property="VerticalAlignment" Value="Center" /&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>The border never shows up when validation errors occur. Any tips what is going wrong?</p>