Choose the best Client/Server Validation Framework for MVC

Question

Im trying to choose the best server/client validation framework to use with my MVC application. I would like to know what is the best validation framework to use with MVC to do server/client validation.

My options are:

• Castle validator
• Microsoft Data Annotations
• nHibernate Validator

Answer 1

With the upcoming MVC 2, it looks like MS is leaning towards the System.ComponentModel.DataAnnotations library. It's pretty nice - does a lot of code generation for you.

Answer 2

I've been using xVal with great success.

The best thing is you can fully automate validation:

• put DataAnnotations (or special rules) to your business layer POCO classes (if you have them) or entity classes' metadata buddy classes if you use entities up to controller layer
• write an ActionFilter that will automatically validate parameters to your controller actions - it's best if all your POCOs (or entities) implement a certain interface that defines Validate() method, filter calls this method and fills ModelState.Errors when validation fails.
• Add if (ModelState.IsValid) { ... } in your controller action that needs to work differently when model isn't valid
• Put <%= Html.ValidationMessage(...) %> in your views that will display validation errors
• Add xVal's client validation to your views if desired

This way you've set up automatic object validation. All your controller actions will do is check Model validity.

Asp.net MVC 2 will have something very similar to xVal already built in the framework so it's up to you which version are you using.