Similar windows (WPF) sharing the same methods

In winforms I could just use a base class (form) that has all the methods I would like the derived classes to use but since WPF prohibits 'visual' inheritance how can I do the same 'method' inheritance?

For instance Window1 and Window2 could call a method "Clear" which will clear all the controls in the Window.

EDIT:
Found this and will try it out later but suggestions are still very much welcome!