Disabling Request Validation in MVC

public class MyModelclass {
    [AllowHtml]
    public string FirstName{ get; set; }
    public string LastName { get; set; }
}
[ValidateInput(false)]
public class MyController : Controller {
    public ViewResult ShowName() {
        return View(new MyModelclass { firstName = "" },firstName = "" );
    }

    [HttpPost]
    public ViewResult RegisterName(MyModelclass name) {

        if (ModelState.IsValid) {
            repository.SaveName(name);
            return View("Completed", name);
        } else {
            return View();
        }
    }
}