创建一个全局变量  

Public double Sumdb;

private void DataGrid1_ItemCreated(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)

         {            

              ListItemType lit=e.Item.ItemType;

              if(lit==ListItemType.Footer)

              {

                   TableCell tc1=e.Item.Cells[3];

                   TableCell tc2=e.Item.Cells[4];

                   TableCell tc3=e.Item.Cells[5];

                   TableCell tc4=e.Item.Cells[6];

                   Label L_xj=new Label();

                   L_xj.ID="lb_xj";

                   L_xj.Width=30;

                   L_xj.Text="合计";

                   tc1.Controls.Add(L_xj);

                   Label L_SumData=new Label();

                   L_SumData.ID="L_SumData";

                   L_SumData.Width=30;

                   L_SumData.Text=SumData();

                   tc2.Controls.Add(L_SumData);

Label L_zj=new Label();

                   L_zj.ID="lb_zj";

                   L_zj.Width=30;

                   L_zj.Text="总合计";

                   tc1.Controls.Add(L_zj);

                   Label L_SumPage = new Label();

                   L_SumPage.ID=”l_sumPage”;