用DropDownList实现的省市级三级联动

这是一个用DropDownList 实现的省市级三级联动，记录一下········

 <asp:ScriptManager ID="ScriptManager1" runat="server">/asp:ScriptManager>

<asp:UpdatePanel ID="UpdatePanel1" runat="server">

                         <ContentTemplate>

					<p><span class="redcolor">* </span>选择地区：

                                                <asp:DropDownList ID="ProvinceSelect" AutoPostBack="True"  runat="server" OnSelectedIndexChanged="GetCityName_onClick">

						</asp:DropDownList>

						<asp:DropDownList runat="server" ID="CitySelect" AutoPostBack="True" OnSelectedIndexChanged="Getcounty_OnClick"  >

						</asp:DropDownList>

						<asp:DropDownList   AutoPostBack="True" runat="server" ID="County">

						</asp:DropDownList>

					</p>

                       </ContentTemplate>

                         <Triggers>

                            <asp:AsyncPostBackTrigger ControlID="ProvinceSelect" EventName="SelectedIndexChanged" />

                        </Triggers>
</asp:UpdatePanel>

后台代码：

protected void Page_Load(object sender, EventArgs e)

        {

            if (!IsPostBack)

            {

                ProvinceSelect.DataSource = BFL.GetPrivoces();

                ProvinceSelect.DataTextField = "RegionName";

                ProvinceSelect.DataValueField = "RegionId";

                ProvinceSelect.DataBind();

                ProvinceSelect.Items.Insert(0, new ListItem("请选择", string.Empty));

                CitySelect.Items.Insert(0, new ListItem("请选择", string.Empty));

                County.Items.Insert(0, new ListItem("请选择", string.Empty));

            }

        }

        #region 省市县数据绑定

        //市级绑定

        public void GetCityName_onClick(object sender, EventArgs e)

        {

            CitySelect.DataSource = BFL.GetCitys(int.Parse(ProvinceSelect.SelectedItem.Value));

            CitySelect.DataTextField = "RegionName";

            CitySelect.DataValueField = "RegionId";

            CitySelect.DataBind();

            County.Items.Insert(0, new ListItem("请选择", string.Empty));

        }

        //县级绑定

        public void Getcounty_OnClick(object sender, EventArgs e)

        {

            County.DataSource = BFL.GetCitys(int.Parse(CitySelect.SelectedItem.Value));

            County.DataTextField = "RegionName";

            County.DataValueField = "RegionId";

            County.DataBind();

            County.Items.Insert(0,new ListItem("请选择",string.Empty));

        }

        #endregion