private void voidInvoice_Click(object sender, EventArgs e) { DialogResult result = MessageDialog.Show("Delete Invoice!", "Are you sure want to delete invoice", "warning"); if (result == DialogResult.Yes) { if (checkForInvoice()) { InvoiceItemModel invitem = new InvoiceItemModel(); invitem.delete(invitem, "invoice_id='" + this.inv.id + "'"); PaymentModel payment = new PaymentModel(); payment.delete(payment, "invoice_id='" + this.inv.id + "'"); inv.delete(this.inv); resetInvoice(false); } } }