在GridView模板列内的DropDownList,如何绑定树形数据

Question

数据库结构

nodeid 代码
name 名称
parentid 父ID


前台aspx文件

HTML code

…………
<form id="form1" runat="server">
<asp:GridView ID="GridView1" RowDataBound="GridView1_RowDataBound" runat="server" AutoGenerateColumns="False">
    <Columns>
        <asp:BoundField HeaderText="第一列" />
        <asp:BoundField HeaderText="第二列" />
        <asp:BoundField HeaderText="第三列" />
        <asp:BoundField HeaderText="第四列" />
        <asp:BoundField HeaderText="第五列" />
        <asp:TemplateField HeaderText="模板列">
        <ItemTemplate>
        <asp:DropDownList ID="DropDownList1"runat="server"></asp:DropDownList>
        </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>
</form>
…………

后台C#

C# code

protected void GridView1_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e)
   {
       DropDownList drop = e.Row.FindControl("DropDownList1") as DropDownList;
      …………//此处该如何写代码？
//将数据库中的树形数据绑定在DropDownList1中

       
   }