NOOB Challenge Implementing MVVM in WPF

Question

To preface, this is my first attempt at MVVM... I buy it, I'm just having a little trouble implementing it.

I'm building a utility to assist with managing a course. I have a COURSE object which contains a few properties and methods as well as a collection of MODULES. Each module has a few properties, methods and a reference to a PRESENTATION object and LAB object (each of those has a few properties. I first implemented the modele and wrote all unit tests.

My challenge is now in implemting the UI (V & VM)... specifically the view-model part of the MVVM.

The UI allows you to create a course, see the modules and then have a master-detail view into each module where you can set a few properties and such. For my view model, I created an object to encapsulate the COURSE model... exposing a few properties including an ObserveableCollection of the course modules.

I've run into a few things that are throwing me for a loop and looking for some help:

1. I'm not sure if I went about my VM part correctly by creating something that encapsulates the COURSE model. Because I need to access MODULES in the course as well as LABs and PRESENTATIONs in the COURSE object. Does that mean I need to create VM's for each of those as well? Seems like I'm going about this the wrong way as this approach means I'm going to encapsulate every object in the model, same goes for each method and property?
2. When showing the modules in the UI of the app, I need to move things up and down in the order. The methods that do this are baked into the COURSE model. The trick is when I use these methods from the view, it isn't updating the view because the courses object lives in the VM, not in the M. I can "fix" this by setting the DataContext of my listview to null and then resetting it to be the same as the hosting window (which is the COURSE), but that isn't ideal. The modules are an observable collection, but they won't update because I'm doing the work at a lower level.

Seems I'm going about my VM a bit wrong... something tells me that not everything from the model should be encapsulated within it.

Answer 1

1. You don't NEED to create VMs for Modules or Labs, having Observable collections of each is enough. But...If you need to have extra powers on each of these objects, you can have collections of ViewModels instead. (as the Josh Smith example do)
2. If your logic is in the model, you need to refresh the ViewModel when you do changes to the model.