如何在前台取得异步绑定的DropdownList某项值

Mido5296889 2010-09-17 11:35:01

最近刚学习ASP.NET AJAX，好不容易实现了省、地市、地区三个下拉列表联动功能，其中地市、地区信息是从后台异步获取的，可是问题又来了，现在想从前台通过JS取得地市或者地区下拉列表中的某项值以便做进一步判断，可是由于数据时异步获取，html页面中无法找到列表绑定的值，请高手赐教，给点解决思路也行。大致代码如下：

<asp:DropDownList ID="drpProvince" runat="server" onselectedindexchanged="drpProvince_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>

            <asp:UpdatePanel ID="UpdatePanel1" runat="server" RenderMode="Inline" UpdateMode="Conditional">

                <ContentTemplate>

                       <asp:DropDownList ID="drpCity" runat="server" onselectedindexchanged="drpCity_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>

                        <asp:DropDownList ID="drpArea" runat="server"></asp:DropDownList>

                </ContentTemplate>

                <Triggers>

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

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

                </Triggers>

            </asp:UpdatePanel>

后台主要代码：

protected void drpCity_SelectedIndexChanged(object sender, EventArgs e)

        {

            BindAreaData(drpProvince.SelectedItem.Text,drpCity.SelectedItem.Text);

        }



        protected void drpProvince_SelectedIndexChanged(object sender, EventArgs e)

        {

            BindCityData(drpProvince.SelectedItem.Text);

        }





        private void BindCityData(string province)

        {

            drpCity.Items.Clear();

            drpCity.Items.Add(new ListItem("请选择地市", "0"));



            DataTable dt = 数据集;



            for (int i = 0; i < dt.Rows.Count; i++)

            {

                drpCity.Items.Add(new ListItem(dt.Rows[i]["city"].ToString(), ""));

            }

        }