What's the point of having models in WPF?

Question

So far I have yet to see the value of having models in WPF. All my ViewModels, by convention, have an associated Model. Each of these Models is a virtual clone of the their respective ViewModel. Both the ViewModel and Model classes implement INotifyPropertyChanged and the ViewModel just delegates everything to the Model anyway.

Why bother having Models then? Why can't I just move my Model logic up into the ViewModel and call it a day?

It seems rather redundant (that is, not DRY) to have MVVM, and just use VVM by default unless some special edge case demands a Model.

If using explicit model classes better supports unit testing, for example, or some other best practice, I can see the value.

Answer 1

The model is just the low level application data.

The view model is more specific.

• It's like a window tapping into the data tailored for the view.
• It also augments the model with details needed for the view. A good example is pagination.
• A model can have more than one view model. These view models would offer different aspects of the data.
• You can create a mashup of different data sources. A view model cleanly façades the models involved.

That means there is no 1:1 relationship between models and view models.

So, if you just display the low level data without a lot of additional logic, features, summaries, aggregations, filters, etc. you can do away with view models and just use the model directly. This seems to be the case with your project.

Answer 2

The model can be auto-generated (Entity Framework), or it might not be a specific class at all (think of a DataTable).

I assume that if you say "I don't use a model", you do in fact use a model, you just don't call it that way.