ASP.NET中使用DropDownList实现无刷新二级联动详细过程

Demo.sql

 create table Car(
     [id] int identity,
     [brand] varchar(50) not null,
     [type] varchar(50) not null
 )
 go

 insert into Car ([brand],[type])values('BMW','B'),('BMW','M'),('BMW','W'),
     ('BENZ','B'),('BENZ','E'),('BENZ','N'),('BENZ','Z'),
     ('HONDA','H'),('HONDA','O'),('HONDA','N'),('HONDA','D'),('HONDA','A'),
     ('TOYOTA','T'),('TOYOTA','O'),('TOYOTA','Y'),('TOYOTA','A')

Demo.aspx

         <asp:ScriptManager runat="server">
         </asp:ScriptManager>
         <asp:UpdatePanel runat="server">
             <ContentTemplate>
                 <asp:DropDownList ID="dropBrand" runat="server" OnSelectedIndexChanged="dropBrand_SelectedIndexChanged"
                     Width="" AutoPostBack="True">
                 </asp:DropDownList>
                 <asp:DropDownList ID="dropType" runat="server" Width="">
                 </asp:DropDownList>
             </ContentTemplate>
         </asp:UpdatePanel>

Demo.aspx.cs

         protected void Page_Load(object sender, EventArgs e)
         {
             if (!IsPostBack)
             {
                 BindDrop();
             }
         }

         private void BindDrop()
         {
             //将数据捆绑到下拉列表中
             string sqlStr = "select distinct [brand] from Car";
             DataTable dt = SqlHelper.ExecuteDataTable(sqlStr);
             dropBrand.DataTextField = "brand"; //设置列表显示的字
             dropBrand.DataValueField = "brand"; //设置列表提交后获得的字段，自己理解为隐藏绑定数据
             dropBrand.DataSource = dt;
             dropBrand.DataBind();
             dropBrand.Items.Insert(, new ListItem("请选择车子品牌", ""));//第一项中加入内容,重点是绑定后添加
             dropType.Items.Insert(, new ListItem("请选择车子品牌型号", ""));//第一项中加入内容,重点是绑定后添加
         }

         protected void dropBrand_SelectedIndexChanged(object sender, EventArgs e)
         {
             string sqlStr = "select * from Car where [brand]='" + dropBrand.SelectedValue + "'";//页面加载后dropBrand.DataValueField隐藏绑定的数据，后边根据它查询dropType要显现的数据
             DataTable dt = SqlHelper.ExecuteDataTable(sqlStr);
             dropType.DataTextField = "type"; //设置dropBrand事件SelectedIndexChanged改变后dropType列表显示的数据
             dropType.DataValueField = "id";
             dropType.DataSource = dt;
             dropType.DataBind();
         }

参考原文：http://www.cnblogs.com/cqchai/archive/2011/05/28/2061378.html