Open Window, Dialog or Message Box from a ViewModel – part 2

In my previous post I have shown how to open a Window bound to a view-model triggered by the view, using a simple Action. In this post I'll show how to open a Window, triggered by the view-model. Opening a window directly by the view where the view decides when a Window should be opened, is an incorrect approach since the view shouldn't make that decision. This decision belongs to the Application