title: Bind the error data of datagridrow to a tooltip textblock
body: <p>I am trying to show the validation error message of data grid row in a tooltip. Here is the code that works when I use the ToolTip property of the Grid control directly (wihtout styling):</p>
  
  <pre><code>&lt;Grid Margin="0,-2,0,-2" ToolTip="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGridRow}}, Path=(Validation.Errors)[0].ErrorContent}"&gt;
                                  &lt;Ellipse StrokeThickness="0" Fill="Red" 
                                           Width="{TemplateBinding FontSize}" 
                                           Height="{TemplateBinding FontSize}" /&gt;
                                  &lt;TextBlock Text="!" FontSize="{TemplateBinding FontSize}" 
                                             FontWeight="Bold" Foreground="White" 
                                             HorizontalAlignment="Center"  /&gt;                            
                              &lt;/Grid&gt;
  </code></pre>
  
  <p>Now this shows the tooltip correctly. Everything is fine.</p>
  
  <p><strong>Problem:</strong></p>
  
  <p>As soon as I start styling the ToolTip separately, the binding stops working somehow. Here is the code that I am trying which does not work:</p>
  
  <pre><code>&lt;Grid Margin="0,-2,0,-2"&gt;
      &lt;Ellipse x:Name="ErrorEllipse" StrokeThickness="0" Fill="Red" 
             Width="{TemplateBinding FontSize}" 
             Height="{TemplateBinding FontSize}" /&gt;
             &lt;TextBlock Text="!" FontSize="{TemplateBinding FontSize}" 
                 FontWeight="Bold" Foreground="White" 
                 HorizontalAlignment="Center"/&gt;
                 &lt;Grid.ToolTip&gt;
                     &lt;ToolTip Background="Transparent" BorderBrush="Transparent" Height="Auto" Width="Auto"&gt;
                         &lt;Border &gt;
                             &lt;TextBlock Text= "{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGridRow}}, Path=(Validation.Errors)[0].ErrorContent}"
                                                         MinHeight="20"
                                                         MinWidth="100"
                                                         Foreground="White"
                                                         Background="Red"/&gt;
                          &lt;/Border&gt;
                      &lt;/ToolTip&gt;
                  &lt;/Grid.ToolTip&gt;
               &lt;/Grid&gt;
  </code></pre>
  
  <p>What am I missing here and how can I achieve the proper binding? Probably its something basic but I have no idea...</p>