title: DataGridCell Validation.ErrorTemplate ignored
body: <p>I'm trying to set the Validation.ErrorTemplate of the DataGridCells, here's the xaml code:</p>
  
  <pre><code>&lt;Style x:Key="{x:Type DataGridCell}"  x:Uid="dataGridCellErrorTemplate" TargetType="{x:Type DataGridCell}"&gt;
      &lt;Setter Property="Validation.ErrorTemplate"&gt;
          &lt;Setter.Value&gt;
              &lt;ControlTemplate &gt;
                  &lt;Border BorderBrush="Green" BorderThickness="2" ToolTip="Heidenei"&gt;&lt;/Border&gt;
              &lt;/ControlTemplate&gt;
          &lt;/Setter.Value&gt;
      &lt;/Setter&gt;
      &lt;!-- following line only for demonstration that the setter is working ... --&gt;
      &lt;Setter Property="Background" Value="Aquamarine"&gt;&lt;/Setter&gt;              
  &lt;/Style&gt;
  </code></pre>
  
  <p>while the background of the datagridcells is successfully colored green (independant from any validation result) the used Validation.ErrorTemplate is still the default one, i.e. the red border.</p>
  
  <p>I know there have been similar issues here in stackoverflow, e.g. 
  <a href="https://stackoverflow.com/questions/7769359/styling-datagridcell-error-template">Styling DataGridCell Error Template</a>
  but they do not really solve my problem.</p>
  
  <p>Any help is appreciated</p>
  
  <p>Frank</p>