请问下图片效果中的后端怎么实现的?

效果图

前端代码

    <asp:DataList ID="DataList1" runat="server" style="margin-top: 10px; margin-left: 20px" Width="600px">
            <ItemTemplate>
               <fieldset>
                  <legend>
                            <asp:CheckBox ID="ckbFirstRole" runat="server" Text='<%# Eval("text") %>' onclick="SelectDept(this);" />
                  </legend>
                  <asp:HiddenField ID="HiddenField1" runat="server" Value='<%# Eval("value") %>' />
                        <asp:CheckBoxList ID="chblRole" runat="server" Style="margin-left: 10px" DataSourceID="ObjectDataSource1" DataTextField="region_name" DataValueField="tax_no" RepeatColumns="8">
                        </asp:CheckBoxList>
                        <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="GetChildRegion" TypeName="HXCRM.BLL.Bregion">
                            <SelectParameters>
                                <asp:ControlParameter ControlID="HiddenField1" Name="node" PropertyName="Value" Type="String" />
                            </SelectParameters>
                        </asp:ObjectDataSource>
                </fieldset>
          </ItemTemplate>
    </asp:DataList> 

我猜测的是,先绑定DataList的DataSource然后在OnItemDataBound中调用ObjectDataSource的select()绑定CheckBoxList数据原,但前台代码中没有OnItemDataBound,就想不通了,有看懂的大哥指点下吧