title: Sticky Group Headers in ListBox
body: <p>I am binding a WPF ListBox to a ICollectionView which is grouped. The ListBox displays correctly with the group headers, but I want to add additional behavior to this.</p>
  
  <p>I want group headers to stick to the top until the next group header causes it to slide out of view.  This is similar to how the IPhone contact list works where the headers, 'A', B', 'C', stick to the top until the next letter category replaces it.</p>
  
  <p><a href="https://i.stack.imgur.com/uXTCc.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uXTCc.jpg" alt="Illustration"></a></p>
  
  <p>I thought this would be a popular feature, but I am not able to find an example of this online.</p>