ASP.NET2.0中GridView嵌套取值的问题！
在GridView1中嵌套了一个GridView4，当点击GridView4中某一行时，怎样才能取到当前GridView4在GridView1中所在的行？？？

<asp:GridView   ID= "GridView1 "   runat= "server "   AutoGenerateColumns= "False "   OnRowDataBound= "GridView1_RowDataBound "   ShowFooter= "True "   OnRowCommand= "GridView1_RowCommand "   DataKeyNames= "type ">
    <Columns>
        <asp:BoundField   DataField= "type "   HeaderText= "type "   />
        <asp:TemplateField   HeaderText= "Case ">
            <ItemTemplate>
            <asp:GridView   ID= "GridView4 "   runat= "server "   AutoGenerateColumns= "False "   ShowFooter= "True "   OnRowDataBound= "GridView4_RowDataBound "   OnRowCommand= "GridView4_RowCommand "   DataKeyNames= "pub_id,type,price,advance ">
                <Columns>
                    <asp:BoundField   DataField= "pub_id "   HeaderText= "Pub_id "   />
                    <asp:BoundField   DataField= "price "   HeaderText= "Price "   HtmlEncode= "False "   NullDisplayText= "0 "   />
                    <asp:BoundField   DataField= "advance "   HeaderText= "Advance "   />
                    <asp:ButtonField   CommandName= "a "   Text= "按钮 "   DataTextField= "type "   />
                </Columns>
            </asp:GridView>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

protected   void   Page_Load(object   sender,   EventArgs   e)
{
        titlesTypeTableAdapter   titlesType   =   new   titlesTypeTableAdapter();
        GridView1.DataSource   =   titlesType.GetTitlesByType();
        GridView1.DataBind();
}
protected   void   GridView1_RowDataBound(object   sender,GridViewRowEventArgs   e)
{
    if   (e.Row.RowType   ==   DataControlRowType.DataRow)
    {
        string   type   =   e.Row.Cells[0].Text;
        titlesTypeTableAdapter   titlesType   =   new   titlesTypeTableAdapter();
        ((GridView)e.Row.Cells[1].FindControl( "GridView4 ")).DataSource   =   titlesType.GetPub_idByType(type);
        ((GridView)e.Row.Cells[1].FindControl( "GridView4 ")).DataBind();
    }
}

protected   void   GridView4_RowCommand(object   sender,   GridViewCommandEventArgs   e)
{
        if   (e.CommandName.CompareTo( "a ")   ==   0)
        {
                int   i   =   0;         //   i表示当前GridView4在GridView1中所在的行；