More Classes

Did you notice something odd about the DependencyProperty and PropertyMetadata classes? They descend directly from Object, not one of the WPF classes like FrameworkElement. I think of them as sitting outside the system in order to manipulate it. (I’m sure the architects of WPF would have a more elegant description.)

But the WPF classes you create will descend, more or less directly, from FrameworkElement, and one of the ancestors of FrameworkElement, the DependencyObject, provides some important functions for creating and working with dependency properties. In fact, DependencyObject, which as you can see sits quite high in the WPF class hierarchy, specifically encapsulates the functionality of objects that participate in the dependency property system.