1     MyDBDataContext context = new MyDBDataContext(); 2     protected void Page_Load(object sender, EventArgs e) 3     { 4         //IsPostBack当前请求是否第一次打开,只有在第一次打开的时候是false，其它时候都是true 5         //在每个Load页面写代码之前，都加上这句话 6         if (!IsPostBack) 7         { 8             ShowProd(); 9             ShowBrand();10             ShowCar();11         }12     }13     /// <summary>14     /// 显示汽车名称15     /// </summary>16     private void ShowCar()17     {18         var q = context.Car.Where(p=>p.Brand==DropDownList2.SelectedValue);19         //绑定显示20         DropDownList3.DataSource = q;21         DropDownList3.DataTextField = "Name";22         DropDownList3.DataValueField = "Code";23         DropDownList3.DataBind();24     }25     /// <summary>26     /// 显示系列名称27     /// </summary>28     private void ShowBrand()29     {30         var q = context.Brand.Where(p=>p.Prod_Code==DropDownList1.SelectedValue);31         DropDownList2.DataSource = q;32         DropDownList2.DataTextField = "Brand_Name";33         DropDownList2.DataValueField = "Brand_Code";34         DropDownList2.DataBind();35     }36     /// <summary>37     /// 显示厂商名称38     /// </summary>39     /// <param name="context"></param>40     private void ShowProd()41     {42         var q = context.Productor;43         DropDownList1.DataSource = q;44         DropDownList1.DataTextField = "Prod_Name";45         DropDownList1.DataValueField = "Prod_Code";46         DropDownList1.DataBind();47     }48     /// <summary>49     /// 下拉列表厂商改变选择时50     /// </summary>51     /// <param name="sender"></param>52     /// <param name="e"></param>53     protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)54     {55         ShowBrand();56         ShowCar();57     }58     /// <summary>59     /// 下拉列表系列改变选择时60     /// </summary>61     /// <param name="sender"></param>62     /// <param name="e"></param>63     protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)64     {65         ShowCar();66     }