, spivonious wrote

*snip*

Who said anything about a single file?

Architect your application so that one instance of the business layer can be accessed from two different viewmodels. If the views are bound to the same instance, then there's no reason to pass data between views.

And remember, even though WPF shines with the MVVM pattern, it is not the only design pattern choice. This particular application may not benefit from separation of the view and the viewmodel.

Good reminder, thank you.