省份+城市---Dropdownlist控件的应用

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>        //防止页面的刷新

<asp:DropDownList ID="drop_sheng" runat="server" AutoPostBack="True" onselectedindexchanged="drop_sheng_SelectedIndexChanged" DataTextField="name" DataValueField="id">
</asp:DropDownList>
<asp:DropDownList ID="drop_qu" runat="server" AutoPostBack="True">
</asp:DropDownList>

</ContentTemplate>
</asp:UpdatePanel>

protected void Bindshengfen()
{
drop_sheng.DataSource = DB.GetDataSet("id,name", "shengfen", "parentid=0", "id asc");
drop_sheng.DataTextField = "name";
drop_sheng.DataValueField = "id";
drop_sheng.DataBind();
drop_sheng.Items.Insert(0, new ListItem("省份", ""));
}
protected void Binddiqu()
{
drop_qu.DataSource = DB.GetDataSet("id,name", "chengshi", "parentid=‘" + drop_sheng.SelectedValue.ToString() + "‘", "idasc");
drop_qu.DataTextField = "name";
drop_qu.DataValueField = "id";
drop_qu.DataBind();
drop_qu.Items.Insert(0, new ListItem("城市", ""));
}
protected void drop_sheng_SelectedIndexChanged(object sender, EventArgs e)
{
Binddiqu();
}