title: WPF Conditional Binding. Button.IsEnabled to SelectedIndex >= 0
body: <p>I want to bind a buttons <code>IsEnabled</code> property to a condition like <code>myObject.SelectedIndex &gt;= 0</code>. Is there a simple way to do this in the xaml (without having to do crazy things to any underlying objects)? I haven't really seen a good example.</p>
  
  <p>Honestly, I wish this was as easy as Flex 3 ... I.E.:</p>
  
  <pre><code>&lt;mx:Button enabled="{dataGrid.SelectedIndex &gt;= 0}" ...
  </code></pre>