比如为了实现以下嵌套效果

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代码
           <!--主菜单开始-->
           <ASP:datalist id="Datalist1" runat="server" RepeatDirection="Horizontal" RepeatColumns="1"
            Width="100%" OnItemDataBound="Datalist1_ItemDataBound">
            <ItemTemplate>
             ★<a href='product_type_detail.aspx?id=<%# DataBinder.Eval(Container.DataItem,"typeid") %>'>
             <%# DataBinder.Eval(Container.DataItem,"typename") %></a>★<br/>
             <!--子菜单开始-->
              <asp:datalist id="Datalist2" Width="100%" runat="server" RepeatColumns="3" RepeatDirection="Horizontal">
               <ItemTemplate>
                <a href='product_type_detail.aspx?id=<%# DataBinder.Eval(Container.DataItem,"typeid") %>'>
                     <%# DataBinder.Eval(Container.DataItem, "typename")%></a>                    
               </ItemTemplate>
              </asp:datalist>
             <!--子菜单结束-->
            </ItemTemplate>
           </asp:datalist>
           <!--主菜单结束-->
后台：
（1）为主DataList绑定主数据。
        void MyBind()
        {
            DBHelper helper = new DBHelper();
            string sql = "select typeid,pid,typename from product_type where typelevel=1 order by ordernum ";
            DataSet ds = new DataSet();
            ds = helper.ExecuteDataSet(sql);
            Datalist1.DataSource = ds;
            Datalist1.DataBind();
        }
（2）为子DataList绑定数据。
DataList嵌套的重点是要在外层DataList的ItemDataBound事件中完成对嵌套DataList的绑定。在主DataList的ItemDataBound事件中用e.Item.FindControl方法来找到嵌套层DataList的id,完后为该id绑定数据
        protected void Datalist1_ItemDataBound(object sender, DataListItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                DataList Datalist2 = (DataList)e.Item.FindControl("Datalist2");
                DataRowView rowv = (DataRowView)e.Item.DataItem;
                int pid = Convert.ToInt32(rowv["typeid"]);
                if (pid > 0)
                {
                    DBHelper helper = new DBHelper();
                    string sql = "select typeid,pid,typename from product_type where pid=" + pid;
                    DataSet ds = new DataSet();
                    ds = helper.ExecuteDataSet(sql);
                    if (ds != null)
                    {
                        try
                        {
                            Datalist2.DataSource = ds;
                            Datalist2.DataBind();
                        }
                        catch (Exception ex)
                        {
                            throw new Exception(ex.Message);
                        }
                    }
                }
            }
        }