Sometimes you need to use the databinding with an object that you have not created and you can't use inheritance.
For example I wanted to use a Mogre Camera and build some WPF animation with it and I couldn't because :
WPF animation needed a DependencyProperty to manipulate,
I couldn't derive the Mogre.Camera class and add it the correct things because I got the camera from a factory object (the sceneManager).
Then I couldn't use the WPF animation to move my camera... next is how I solve it.