MVVM Child models and Navigation and beer

Question

i was at the bar and i had couple beers, and this girl was arguing that getting mvvm to work with a real world applications is pain, she said that in order to solve problem

Answer 1

If you want loosely-coupled communication you need an EventAggregator:

//Simplest EventAggregator
public static class DumbAggregator
{
    public static void BroadCast(string message)
    {
       if (OnMessageTransmitted != null)
           OnMessageTransmitted(message);
    }

    public static Action OnMessageTransmitted;
}

Usage:

public class MySender
{
   public void SendMessage()
   {
       DumbAggregator.BroadCast("Hello There!");
   }
}

public class MySubscriber
{
   public MySubscriber()
   {
       DumbAggregator.OnMessageTransmitted += OnMessageReceived;
   }

   private void OnMessageReceived(string message)
   {
      MessageBox.Show("I Received a Message! - " + message);
   }
}

And if you don't like Child ViewModels, you can put everything inside a single ViewModel, and have some DataTriggers or something to dynamically change views, however a Parent - Children ViewModel approach is much cleaner IMO.