Question

Basically, I’m not sure where to start:

I have my Shell.xaml window.
I also have my Popup.xaml window.

I set the Shell.xaml to import the PopupWindow then when the PopupWindow Loaded event fires, it does:

Popup.Owner = this;
Popup.Show();

Now, I need to be able to have the PopupWindow’s ViewModel communicate with the Shell.xaml. Basically, I need to be able to have the PopupWindow tell the Shell’s ViewModel information the user inputs.

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Update:

In keeping this decoupled, I don’t want to pass in any instance of the Client’s viewmodel to the popup, I’d much rather have the Popup’s ViewModel somehow have a way of communicating to the Client’s ViewModel without knowing who it is actually talking to.

Answer 1

Have a look at the event aggregator in Prism. The aggregated events in Prism are intended as a means of facilitating decoupled, inter-viewmodel communication. If you are going for “pure” MVVM, I think that it would go something like this:

• Your ViewModel publishes a message (interaction request) that it want’s to display a popup.
• Your View is listening for the message, and shows the popup window (decouples your viewmodel from understanding how prompts are displayed)
• Your ViewModel gets the results of the popup window (your popup window is just a view, and should know nothing about raising aggregate events)
• Your ViewModel raises a Prism Aggregate Event (an object containing the user input is the payload)
• Your shell is listening for that event.