MVC3 Architecture/Validation Question

I think this is a pretty simple task, but I can't for the life of me get it working.

Environment - MVC3, FluentValidation, StructureMap.

I have a ViewModel (RegisterViewModel) that has the following attributes { Email, IsBusiness, BusinessContact }. Email is required a开发者_JAVA百科lways, BusinessContact is required if the IsBusiness checkbox is checked.

I was trying to perform the BusinessContact required check client side, but can't for the life of me figure out the right way to do this.

Suggestions?

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You will have to roll your own client side validation to enforce the constraint your looking for. Phil Haack has a great post on how to do this http://haacked.com/archive/2009/11/19/aspnetmvc2-custom-validation.aspx

Otherwise you could just enforce the constraint server side and add an error to the ModalState and reload the view.