title: WPF: Binding Visibility by string contents
body: <p>Ok, so here is my XAML:</p>
  
  <pre><code>&lt;TextBlock Text="{Binding Path=InstanceName}"&gt;&lt;/TextBlock&gt;
  </code></pre>
  
  <p>If <code>InstanceName</code> is null or an empty string, I want <code>Visibility="Collapsed"</code>. Otherwise I want <code>Visibility="Visible"</code>. How would I do that?</p>