private void loadList() { PaymentServiceClient payService = new PaymentServiceClient(); if (IDnum == "All") payment = new List<Payment>(payService.GetAllPayments()); else payment = new List<Payment>(payService.GetAllStudentsPayments(IDnum)); gridView.DataSource = payment; GroupDescriptor descriptor = new GroupDescriptor(); descriptor.GroupNames.Add("Student", ListSortDirection.Ascending); this.gridView.GroupDescriptors.Add(descriptor); GridViewSummaryItem summaryItem = new GridViewSummaryItem("Amount", "Total: {0}", GridAggregateFunction.Sum); GridViewSummaryRowItem summaryRowItem = new GridViewSummaryRowItem(); summaryRowItem.Add(summaryItem); this.gridView.SummaryRowsBottom.Add(summaryRowItem); }