Validate and display error messages for fields not in model

For fields like Retype Password, Accept Terms and Conditions 开发者_如何学编程what is the best strategy to validate these fields both on the server and the client?

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I used DataAnnotations and add the required, or other validation attributes. Then I use jQuery (or MS Validation) for client side. All is generated if you do it this way.

If you have fields that are not in your regular model, I create new "view" models that match the view. Make your life easier and do this!