WPF DataTemplate绑定与嵌套在ListBox中的ItemsControl一起使用时不起作用

I have a UserControl that contains a ListBox that is bound to a CollectionViewSource called Data and each item in that collection is displayed in the ListBox using an ItemTemplate. That ItemTemplate is an ItemsControl that is bound to another CollectionViewSource called Rows. Rows stores one or more MyListBoxRow objects. For each object in the Data CollectionViewSource, I get a ListBoxItem which is comprised of ContentPresenters from the Rows CollectionViewSource. I have a UserControl that contains a ListBox th