How do I invoke a modal window from a wpf page?

How do I invoke a modal window from a wpf page? Window.showDialog() makes the window modal when it is invoked from a parent Window, however when invoked from a Page, the modal behaviour disappears. I tried using a PopUp co开发者_开发问答ntrol, but it doesnt appear to be as customizable as a window.

I am not sure how are you calling the window, but calling new Window().ShowDialog() from within a page inside frame, makes the new window modal to the whole application.