title: Setting tooltip to equal content
body: <p>I'm trying to set a data grid's cell's tooltip to be equal to the text inside of a TextBlock in that cell. What I have so far is this:</p>
  
  <pre><code>&lt;Style x:Key="CellStyle" TargetType="{x:Type DataGridCell}"&gt;
          &lt;Setter Property="Template"&gt;
              &lt;Setter.Value&gt;
                  &lt;ControlTemplate TargetType="DataGridCell"&gt;
                      &lt;Grid&gt;                         
                          &lt;TextBlock Margin="2" VerticalAlignment="Center" 
                                  HorizontalAlignment="Left"  TextWrapping="Wrap" &gt;
                              &lt;ContentPresenter Content="{TemplateBinding Property=ContentControl.Content}" /&gt;
                              &lt;TextBlock.ToolTip&gt;
                                  &lt;ContentPresenter Content="{TemplateBinding Property=ContentControl.Content}" /&gt;
                              &lt;/TextBlock.ToolTip&gt;
                          &lt;/TextBlock&gt;
                      &lt;/Grid&gt;
                  &lt;/ControlTemplate&gt;
              &lt;/Setter.Value&gt;
          &lt;/Setter&gt;            
      &lt;/Style&gt;
  </code></pre>
  
  <p>However, what this does is very briefly show the tooltip and then the content in the cell is removed, so nothing shows up at all. Also, setting the tooltip from outside the Template setter is an option, but I'm not sure what the corrent binding is to do that.</p>