Where do you do your validation? model, controller or view

Question

Where do you put user input validation in a web form application?

1. View: JavaScript client side
2. Controller: Server side language (C#...)
3. Model

Answer 1

Simple input validation in the view. Full validation in the model. Reason? If you change your view technology, and the validation is in the view/controller, you have to rewrite your validation for the new view. This can introduce bugs. Put it in the model, and this is reused by all views...

But, as I said, simple validation in the view for speed and ease.