When should I use a UserControl instead of a Page?

Question

I notice that many of the WPF MVVM frameworks seem to avoid using the NavigationWindow and Page controls in favor of composing pages using nested UserControls.

The

Answer 1

I just discovered another difference between UserControls and Pages: Pages cannot be used as DataTemplates.

For example, if you were creating application using the MVVM style, you might expect this to work:

But if the ProjectDashboardView is a Page, it will fail.