public int AddStudentSubject(StudentSubject studentSubject)
        {
            StudentSubjectDao = new StudentSubjectDao();

            //convert from business object to data access object

            DataAccess.Domain.StudentSubject studentSubjectData = new DataAccess.Domain.StudentSubject { UserId = studentSubject.UserId, SubjectName = studentSubject.SubjectName, SubjectCode = studentSubject.SubjectCode, AssignmentName = studentSubject.AssignmentName, SubjectDescription = studentSubject.SubjectDescription, Assignment = studentSubject.Assignment, AssignmentSize = studentSubject.AssignmentSize };

            return StudentSubjectDao.AddStudentSubject(studentSubjectData);
        }