title: How to add a StringFormat to a Textblock inside a DataTemplate?
body: <p>I have the following <code>DataTemplate</code>:</p>
  
  <pre><code>&lt;DataTemplate x:Key="ColoringLabels"&gt;
      &lt;TextBlock Padding="0"
                 Margin="0"
                 Name="Username"
                 Text="{Binding Username}"
                 Foreground="Gray"
                 FontStyle="Italic"
                /&gt;
      &lt;DataTemplate.Triggers&gt;
          &lt;DataTrigger Binding="{Binding IsLoggedIn}" Value="True"&gt;
              &lt;Setter TargetName="Username" Property="FontSize" Value="14"/&gt;
              &lt;Setter TargetName="Username" Property="Foreground" Value="Green"/&gt;
              &lt;Setter TargetName="Username" Property="FontStyle" Value="Normal"/&gt;
          &lt;/DataTrigger&gt;
      &lt;/DataTemplate.Triggers&gt;
  &lt;/DataTemplate&gt;
  </code></pre>
  
  <p>I would like to use the template in a <code>ListView</code> where every username is followed by a ; and a space.</p>
  
  <p>Effectively the template would then behave as it were written like this:</p>
  
  <pre><code>&lt;DataTemplate x:Key="ColoringLabels"&gt;
      &lt;TextBlock Padding="0"
                 Margin="0"
                 Name="Username"
                 Text="{Binding Username, StringFormat='{}{0}; '}"
                 Foreground="Gray"
                 FontStyle="Italic"
                /&gt;
      &lt;DataTemplate.Triggers&gt;
        ...
      &lt;/DataTemplate.Triggers&gt;
  &lt;/DataTemplate&gt;
  </code></pre>
  
  <p>How can I extend the original template to get the result of the second one?</p>