Why doesn ListBox derive from Selector?
On WPF, ListBox derives from the Selector class which derives from ItemsControl; on Silverlight, ListBox derives directly from ItemsControl. To simplify matters and keep development/testing/download costs down, the Selector class was thought to be unnecessary for Silverlight 2 Beta 1. With ListBox being the only Selector-derived class in the Beta 1 controls offering, the Selector functionality was merged into ListBox for compactness. (If a Selector class is introduced to the Silverlight controls in the future, it should have little/no effect on existing ListBox code.
