public double GetBalanceByStudentCardId(int cardid)
        {
            int studentId;

            try
            {
                studentId = StudentsManager.GetStudentIdByCardId(cardid);
            }
            catch (ApplicationException ex)
            {
                return(-1);
            }
            return(TransactionsDB.GetBalanceByStudentId(studentId));
        }
        public double GetBalanceByStudentUsername(string username)
        {
            int studentId;

            try
            {
                studentId = StudentsManager.GetStudentByUsername(username);
            }
            catch (ApplicationException ex)
            {
                return(-1);
            }
            return(TransactionsDB.GetBalanceByStudentId(studentId));
        }
 public double GetBalanceByStudentId(int id)
 {
     return(TransactionsDB.GetBalanceByStudentId(id));
 }