// chi cho sua ten nguoi phat hanh hoa don
        public static void updateInvoice(Invoice invinfo)
        {
            int inv_index = MyInvoice.find_InvIndex(invinfo.invNo);

            MyInvoice.myinv[inv_index].invNo          = invinfo.invNo;
            MyInvoice.myinv[inv_index].invType        = invinfo.invType;
            MyInvoice.myinv[inv_index].invTotalAmount = invinfo.invTotalAmount;
            MyInvoice.myinv[inv_index].issueDate      = invinfo.issueDate;
            MyInvoice.myinv[inv_index].invStatus      = invinfo.invStatus;
            MyInvoice.myinv[inv_index].Issuer         = invinfo.Issuer;
            Invoicerw.Invoiceupdate(invinfo, inv_index);
        }
        public static void deleteInvoice(Invoice invinfo)
        {
            int        inv_index    = MyInvoice.find_InvIndex(invinfo.invNo);
            List <int> invdtl_index = MyInvoice.find_InvdtlIndex(invinfo.invNo);

            for (int i = 0; i < invdtl_index.Count; i++)
            {
                MyInvoice.myinvdt.Remove(MyInvoice.myinvdt[invdtl_index[i]]);
            }
            MyInvoice.myinv.Remove(MyInvoice.myinv[inv_index]);
            Invoicerw.Invoicedtldelete(invdtl_index);
            Invoicerw.Invoicedelete(inv_index);
        }