To investigate - how to handle ListBoxes which mix ListBoxItems with visuals that are not ListBoxItem

[vchelaru]

Currently the code assumes that the index of the newly-added visual is the same as the index of the ListBoxItem in the ListBox's ListBoxItemsInternal. If a non-ListBoxItem is inserted, what do we do?

One option is to wrap all framework elements in listbox items, but that would mean clicking on something like a separator would de-select other ListBoxItems, or would raise events to close. I don't think we want that...