datagrid 在页脚统计

private void DataGrid1_ItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {            
            if ( e.Item.ItemIndex >= 0 )
            {
                if ( e.Item.Cells[1].Text.ToString().Trim() != " " ) //如果数据不为空
                {
                    countnum += double.Parse(e.Item.Cells[1].Text);//统计求和
                }
                if ( e.Item.Cells[2].Text.ToString().Trim() != " " ) //如果数据不为空
                {
                    countsize += double.Parse(e.Item.Cells[2].Text.TrimEnd('M'));//统计求和
                }
            }

            if(e.Item.ItemType==ListItemType.Footer)
            {
                e.Item.Cells[0].Text = "合计";
                e.Item.Cells[1].Text = countnum.ToString();
                e.Item.Cells[2].Text = countsize.ToString()+"M";
            }
        }