How to call method in window (.xaml.cs) from viewmodel (.cs) without introducing new references in wpf

Question

I'm looking for a simple way to call a method in my Main Window, but I want to call it from my View Model. Basically, I'm looking for some king of "this.parent" sort of thing to put in the View Model to reference the Main Window.

Or, if you want to check out the reason I want to do this and tell me another way to go about my problem:

I'm working with an app that constantly gets information fed to it. In the viewmodel, the information is processed. I want to make a notification every time a piece of information comes in that satisfies some qualification.

Initially, I had a dictionary in the viewmodel that stored info about that information, and I accessed that dictionary in the MainWindow so that I could make the window flash and send other notifications. But I was getting issues with the viewmodel's dictionary being continuously changed while I was accessing it in the MainWindow.

Sorry if this question sounds stupid. I just started with WPF two months ago, and didn't have a great background in programming even before that, either.

Answer 1

VM should "know" nothing of your View or Window, the way VM typically "communicates" with V in WPF/MVVM is by rasing events. That way VM remains ignorant of/decoupled from the V and since VM is already DataContext of V it's not hard to subscribe to VM's event.

Example:

VM:

public event EventHandler<NotificationEventArgs<string>> DoSomething;
...
Notify(DoSomething, new NotificationEventArgs<string>("Message"));

V:

var vm = DataContext as SomeViewModel; //Get VM from view's DataContext
if (vm == null) return; //Check if conversion succeeded
vm.DoSomething += DoSomething; // Subscribe to event

private void DoSomething(object sender, NotificationEventArgs<string> e)
{
    // Code    
}