参考
 <asp:GridView ID="GridView1"  OnRowDataBound="GridView1_RowDataBound"  AutoGenerateColumns=false runat="server">
      <Columns>
       　<asp:TemplateField>
       　<ItemTemplate> 
           <%#Container.DataItem.ToString()%>
               <!--第二层GridView开始-->
               <asp:GridView ID="GridView2" OnRowDataBound="GridView2_RowDataBound"   AutoGenerateColumns=false runat="server">          
                　<Columns>
                 　<asp:TemplateField>
                 　<ItemTemplate> 
                      <%#Container.DataItem.ToString()%>
                       <!--第三层GridView开始-->
                     　<asp:GridView ID="GridView3"  AutoGenerateColumns=false runat=server>
                           <Columns>
                             <asp:TemplateField>
                             <ItemTemplate> 
                              <%#Container.DataItem.ToString()%>
                             </ItemTemplate>
                             </asp:TemplateField>                    
                           </Columns>
                        </asp:GridView>
                       <!--第三层GridView 结束-->
                       
                   </ItemTemplate>
                  </asp:TemplateField>
                 </Columns>
                </asp:GridView>
              <!--第二层GridView结束-->
              
          </ItemTemplate>
          </asp:TemplateField>
         </Columns>
        </asp:GridView>
         <!--第一层GridView结束-->



++++++++++.cs代码++++++++++++++++
RowDataBound与1.x中的ItemDataBound也有一腿!
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        this.GridView1.DataSource = Al("GridView1Item:");
        this.GridView1.DataBind();
    }

    //DataSource
    protected ArrayList Al(string GetStr)
    {
        ArrayList al = new ArrayList();
        for(int i=0;i<2;i++)
        {
            al.Add(GetStr+i.ToString());
        }

        return al;
    }


    //GridView1_RowDataBound
    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            GridView gv = (GridView)e.Row.FindControl("GridView2");
            gv.DataSource = Al("GridView2Item:");
            gv.DataBind();
            
        }
    }

    //GridView2_RowDataBound
    protected void GridView2_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            GridView gv = (GridView)e.Row.FindControl("GridView3");
            gv.DataSource = Al("GridView3Item:");
            gv.DataBind();

        }
    }
}