The silverlight forums have this exact same question and a great solution for it: http://www.telerik.com/community/forums/silverlight/window/handle-click-outside-window-in-showdialog.aspx#0
However, the solution doesn't work in WPF.
Basically I need to be able to close the RadWindow if the user clicks outside of it. For the silverlight version, the canvas that covers the application is exposed and I can attach a MouseLeftButtonDown event handler to it. I haven't been able to do this for the WPF version because none of the accessible parents are the background where a user would click. The parents of the RadWindow are ContentPresenter, AdornerPresenter, Border, and then InternalWindow (I can't access InternalWindow).
Thanks in advance!