What’s the best way to implement field validation using ASP.NET MVC? [closed]

Take a look at the JQuery Validation plugin this plugin is amazing,it’s clean to implement and has all the features you could ever need, including remote validation via AJAX.

Also a sample MVC controller method can be found here which basically uses the JsonResult action type like:

public JsonResult CheckUserName(string username)
{
    return Json(CheckValidUsername(username));
}