Question

I want to open a window from my ViewModel.
How can I create and show it using Galasoft Messenger?

public partial class View {
    public View() {
        InitializeComponents();
        //Register Open message
    }

    //This is called when ViewModel sends a message
    public void OpenView() {
        new View().Show();
    }
}

public class ViewModel {
    public ViewModel() {
        //Send message to open some view
    }
}

Answer 1

This situation does not require an object to be passed from ViewModel to View; therefore, just registering of type object, passing null, BUT the token is key.

public partial class View {
    public View() {
        InitializeComponents();
        //Register Open message BEFORE ViewModel calls Messenger.Default.Send
        Messenger.Default.Register<object>(this, ViewModel.OpenViewToken, p => { OpenView(); });
    }

    //This is called when ViewModel sends a message
    public void OpenView() {
        new View().Show();
    }
}

public class ViewModel {
    public static readonly Guid OpenViewToken = Guid.NewGuid();
    public ViewModel() {
        Messenger.Default.Send<object>(null, OpenViewToken);
    }
}