title: Reverse bool value in binding
body: <p>I have a <code>TextBlock</code> like this:</p>
  
  <pre><code>&lt;TextBlock Visibility="{Binding IsOnline, Converter={StaticResource boolToVisibilityConverter}}"&gt;
  </code></pre>
  
  <p><code>boolToVisibility</code> returns <code>Visible</code> if <code>IsOnline</code> is true. But in a situation I want textblock be <code>Collapsed</code> if <code>IsOnline</code> is true. </p>
  
  <p>I can make another converter which acts in reverse, but I want to know isn't it possible to do that in XAML with current converter?</p>