public void UpdateAmount(double cost) { try { using (var db = new VendMachineDbContext()) { Account Account = db.Accounts.Where(x => x.CardNO == cardNo).FirstOrDefault(); Account.Amount -= cost; db.Entry(Account).State = EntityState.Modified; db.SaveChanges(); log.Info("Payment success"); } } catch (Exception) { log.Error("Db connection failed"); } }