public void Update(string id)

        {

            Northwind.Models.NorthwindDataContext dc = new NorthwindDataContext();

       //从数据库中取出参数id所对应的的一个Customer记录：

            Customer cust = dc.Customers.Single(c => c.CustomerID == id);

      //将Edit View中的用户的更改赋值到cust对象:

            BindingHelperExtensions.UpdateFrom(cust, Request.Form);

            dc.SubmitChanges();

            RedirectToAction("Index");//跳转到Index View

        }