MVVM: Thin ViewModels and Rich Models

Question

I\'m continuing to struggle with the MVVM pattern and, in attempting to create a practical design for a small/medium project, have run into a number of challenges. One of t

Answer 1

I think INotifyPropertyChanged on your model is only useful when you're expecting it to be operated on by your VM and external "forces" simultaneously.

I'm personally a supporter of POCO models. Putting any framework-specific scaffolding into my model would make me worry. When you put an event into your model class you have to consider carefully possible issues with your model's life-cycle, serialization, storage etc. For example what happens if you recreate your object from data source and old INotifyPropertyChanged subscriptions are now invalid?

Similarily better place for ObservableCollection is in the VM, which can consume an IEnumerable datasource, and present to the view only selected or ad hoc filtered items.