public bool billPaid(int BillId)
        {//upates balance onhand ; bill can not be modified now.
         //If bill is already paid ; error
            bill_master v = (from x in dc.GetTable <bill_master>()
                             where x.billid == BillId
                             select x).SingleOrDefault();

            var abc = (from x in dc.GetTable <case_master>()
                       where x.caseid == v.caseid
                       select x).SingleOrDefault();

            abc.isactive = "no";
            dc.SubmitChanges();

            v.paid = "yes";
            long sal, starting_balance, final_balance;

            sal = v.total;
            starting_balance = getBalance();
            final_balance    = starting_balance + sal;

            cost c = new cost();

            c.date             = DateTime.Now;
            c.starting_balance = starting_balance;
            c.billid           = BillId;
            c.chequeid         = 0;
            c.final_balance    = final_balance;
            setBalance(final_balance);
            dc.costs.InsertOnSubmit(c);
            dc.SubmitChanges();
            return(true);
        }
        //Bills
        public int createBill(int CaseId)
        {
            bill_master b = new bill_master();

            b.caseid = CaseId;
            b.date   = DateTime.Now;
            b.paid   = "No";
            b.total  = 0;
            dc.bill_masters.InsertOnSubmit(b);
            dc.SubmitChanges();
            return(b.billid);
        }
        public bool addItemsToBill(int BillId, int itemid, int qty)
        {
            bill_item bi = new bill_item();

            bi.billid = BillId;
            bi.itemid = itemid;
            bi.qty    = qty;
            dc.bill_items.InsertOnSubmit(bi);
            dc.SubmitChanges();

            bill_master bil = (from x in dc.GetTable <bill_master>()
                               where x.billid == BillId
                               select x).SingleOrDefault();
            item cos = (from x in dc.GetTable <item>()
                        where x.itemid == itemid
                        select x).SingleOrDefault();

            bil.total += (cos.cost_per_item * qty);

            dc.SubmitChanges();

            return(true);
        }