how to add a new row on a web grid in mvc??

Hi Frnds

I am sending to u my code ...but i am stuck in if i click on add button new row is not be add on the web grid in mvc4

please chek the code and give the solution

Model////

public class UserModel
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string LastName { get; set; }

        //public static List getUsers()
        //{
        //    List users = new List();
        //    {
        //        new UserModel();
        //        /*{ ID = 1, Name = "Anubhav", SurName = "Chaudhary" }; */ 
        //    };
        //    users.Add(new UserModel());
        //    //{ ID = 1, Name = "Anubhav", SurName = "Chaudhary" });
        //    return (users);
        //}
        public static List getUsers()
        {
            List users = new List()
            {
              new UserModel (){ ID=4, Name="Jyoti", LastName="Mishra" },
              new UserModel (){ ID=5, Name="Shayli", LastName="Shamra" },
            };
            return users;
        }

    }

Views////

@{
    ViewBag.Title = "Index";
}

WEB GRID

@{
    var grid = new WebGrid(Model);
}

Controller/////

 public ActionResult Index()
        {
            List users = UserModel.getUsers();
            return View(users);
        }