I have two views. One with a RadGridView, the other with a RadListBox. They both have the same view model, and same ItemsSource. I followed the ListBox Grouping and Filtering example. When I have a collection of 2000 items, grouping is noticeably slower in the RadListBox than the RadGridView, i.e. 4 times slower, even when the RadListBox's ItemTemplate contains just a TextBlock. Any idea why this is, and how to speed up grouping in the RadListBox? Thanks.