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="200" AutoPostBack="True">
                </asp:DropDownList>
                <asp:DropDownList ID="dropType" runat="server" Width="200">
                </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(0, 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(0, 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