You are designing an ASP.NET MVC 2 Web application that requires each user to register
a user name and password before accessing restricted content. You have the following
requirements for user registration: • When the focus leaves the user name input field,

validate that the user name does not already exist. • Display validation results before
submitting the form. You need to recommend a data validation strategy. What should you
recommend?

A.
Use the Required attribute to annotate the user name property of the model. Call the
Html.EnableClientValidation() method from the view.

B.
Use an UpdatePanel control to access server-side validation.

C.
Use jQuery to access server-side validation code.

D.
Implement the IValidator interface on the model.