Where do you put your validation in asp.net mvc 3?

Question

One common recommended practice in asp.net mvc is that you should not send your business models to your views.. instead you should create viewmodels specific to each view.

Answer 1

Given that you always pass viewmodels to your view and your domain models are not exposed to the end user through views then i don't see any need for validating domain model itself. For example if you receive PersonViewModel from view through form post you will transform it to Person Model (perhaps through automapper etc.) only if PersonViewModel is valid itself. So i believe that input validations should stay with the view models because they are the one that are bound to input.