title: WPF TextBox.SelectAll () doesn't work
body: <p>I have used the following template in my project:</p>
  
  <pre><code>&lt;DataTemplate 
      x:Key="textBoxDataTemplate"&gt;
      &lt;TextBox 
          Name="textBox"
          ToolTip="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}"
          Tag="{Binding}"
          PreviewKeyDown="cellValueTextBoxKeyDown"&gt;
          &lt;TextBox.Text&gt;
              &lt;MultiBinding
                  Converter="{StaticResource intToStringMultiConverter}"&gt;
                  &lt;Binding 
                      Path="CellValue"
                      Mode="TwoWay"&gt;
                          &lt;Binding.ValidationRules&gt;
                              &lt;y:MatrixCellValueRule 
                                  MaxValue="200" /&gt;
                          &lt;/Binding.ValidationRules&gt;
                  &lt;/Binding&gt;
                  &lt;Binding 
                      RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type y:MatrixGrid}}" 
                      Path="Tag"
                      Mode="OneWay" /&gt;
              &lt;/MultiBinding&gt;
          &lt;/TextBox.Text&gt;
      &lt;/TextBox&gt;
  &lt;/DataTemplate&gt;
  </code></pre>
  
  <p>I used this template to create an editable matrix for the user. The user is able to navigate from cell to cell within the matrix and I would like to highlight the data in the selected textbox but it doesn't work. I called TextBox.Focus () and TextBox.SelectAll () to achieve the effect but nothing. The Focus () works but the text never gets highlighted.</p>
  
  <p>Any help is welcome and appreciated.</p>