两个DropDownList在DataGrid里，后一个随着前一个改变而改变

前台代码如下： 

<asp:DataGrid ID="DataGrid1" runat="server" AllowPaging="True" AutoGenerateColumns="False"
                                        Width="100%" CssClass="colortable">
                                        <FooterStyle CssClass="Table_Foot" />
                                        <EditItemStyle CssClass="Table_Edit" />
                                        <SelectedItemStyle CssClass="Table_Select" />
                                        <PagerStyle CssClass="Table_Page" HorizontalAlign="Center" Visible="False" />
                                        <AlternatingItemStyle CssClass="in3" />
                                        <ItemStyle CssClass="in2" />
                                        <HeaderStyle CssClass="listtop" />
                                        <Columns>
                                              <asp:TemplateColumn HeaderText="目标舍" ItemStyle-CssClass="checkwidth" HeaderStyle-Width="50">
                                                <ItemTemplate>
                                                    <asp:DropDownList runat="server" ID="DropDownListHouseID"    OnSelectedIndexChanged="DropDownListHouseID_SelectedIndexChanged"
                                                        AutoPostBack="true">
                                                    </asp:DropDownList>
                                                </ItemTemplate>
                                            </asp:TemplateColumn>
                                            <asp:TemplateColumn HeaderText="目标栏" ItemStyle-CssClass="checkwidth" HeaderStyle-Width="50">
                                                <ItemTemplate>
                                                    <asp:DropDownList runat="server" ID="DropDownListHurdle">
                                                    </asp:DropDownList>
                                                </ItemTemplate>
                                            </asp:TemplateColumn> 

                                                     </Columns>
                                    </asp:DataGrid>

后台代码如下： 

  protected void DropDownListHouseID_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList dpl = sender as DropDownList;

        object obj = dpl.NamingContainer;
        DataGridItem di = (DataGridItem)dpl.NamingContainer;
        DropDownList dplhurdle = (DropDownList)di.Cells[10].FindControl("DropDownListHurdle");

   
        dplhurdle.DataSource = 数据集

        dplhurdle.DataTextField = ;
        dplhurdle.DataValueField = ;

        dplhurdle.DataBind();
            }