in MVC pass null value and undefine

This is my code

 

 

 

 

 

 

[HttpPost]
public ActionResult AddUser(string Name, string Position, string Office, string Salary)
{
Employee emp=new Employee();
emp.Name = Name;
emp.Position = Position;
emp.Office = Office;
emp.Salary =Convert.ToInt32(Salary);
db.Employees.Add(emp);
db.SaveChanges();
return Json(emp, JsonRequestBehavior.AllowGet);
}