Should I reuse view models in different views?

I would have a seperate ViewModel for each view. Unused properties make the code less readable (Why is that property present if it isn't being used?). If you have the same functionality for a fixed set of properties over several views I could see using a base class which contains those properties.

People tend to have different philosophies of ViewModels based on their perspective of their use. ViewModels are the glue between a view and a model and people will typically base their answer on which of the two ends they like to hold more rigid.

• If you like your model/data objects to be more rigid, then you'll tend to tie the ViewModel closer to the model/data—i.e. you'll have a single ViewModel that is used in multiple views and let the ViewModel determine which properties to retrieve based on how you want to handle data loading (and defer things like images or other long-load properties, etc.).
• If you like your Views to be more rigid, then you'll tie the ViewModel closer to the View—i.e. have a separate ViewModel for each view and let the model/data objects handle things like syncronization as you move from view to view.

Personally, I prefer the first as my data tends to be more rigid because it's less likely to change than the views are (in my projects—I don't think that's a universal property of data and views). Since change notifications are a natural feature of ViewModels, I don't have to make my model objects communicate changes if a user happens to have two views up that show the same/similar data.

In the project I am working on, each view has its own ViewModel, however we also have CollectionViewModels, which are shared/referenced by multiple view models.

Think - a list of Suppliers, that needs to be displayed in multiple screens in your application - and is bound to a variety of controls - a list box, grid view, whatever you need. Having just one ViewModel makes for simpler update/refresh logic of the list of Suppliers.

TLDR: I would only reuse view models, if all usage cases use the ViewModel in the same way. I.e. they all use the same properties etc.