（1）private string filename(string id)
                           
        {
            filename1="";

            string sql = "select classname from texpertspecialclass t,tspecialclass c  Where expertid="+id+" And t.specialclassid=c.specialclassid";
                           
            DataSet ds=(sql);
            filename1="<table widht='100%' border='0'>";
            foreach(DataRow   myRow   in   ds.Tables[0].Rows )
            {   
                filename1 =filename1 + "<tr><td>"+myRow[0] + "</td>";
               
            }        
            filename1 =filename1 + "</table>";                                                                                                               
            GC.Collect();
            
            return filename1;
        }

（2）private void DataGrid1_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {

            if(e.Item.ItemIndex!=-1)
            {
                e.Item.Cells[0].Text=Convert.ToString (e.Item.ItemIndex+1);
               
                e.Item.Cells[2].Text=filename(e.Item.Cells[6].Text);
               
            }
        }

应该生成了一个具有嵌套表格的页面

看了一下,应该是这样吧:
(1)这个方法返回的是一个字符串,字符串中包含一个表格,该表格只包含一列多行...
(2)  e.Item.Cells[2].Text=filename(e.Item.Cells[6].Text);是调用filename()方法,并将GridView中的选中行的cell[2]列置换成filename()方法生成的表格...