How to use WPF elements to call another window without deviating from the MVVM pattern?

Question

WPF

Let's say we have a project with the following content:

-- mainWindow --
|
-> -- views --
    +firstwindow.cs
|
-> -- viewmodels --
    +firstwindowviewmodel.cs

+mainwindow.xaml
+mainwindowviewmodel.cs

How to call firstwindow from mainwindow with such architecture?

Answer 1

Have a service that manages your windows.
Request a service interface in any VM.
Exchange data between windows through another service.