public void UpdateStudentSubjectState(int studentID, int subjectID)
        {
            StudentsSubjects studentSubject = context.StudentsSubjects.FirstOrDefault
                                                  (ss => ss.SubjectID == subjectID && ss.StudentID == studentID);

            if (studentSubject == null)
            {
                studentSubject           = new StudentsSubjects();
                studentSubject.StudentID = studentID;
                studentSubject.SubjectID = subjectID;
                AddStudentSubject(studentSubject);
            }
            else
            {
                DeleteStudentSubject(studentSubject);
            }
        }
 public void AddStudentSubject(StudentsSubjects ss)
 {
     context.Add(ss);
     context.SaveChanges();
 }
 public void DeleteStudentSubject(StudentsSubjects ss)
 {
     context.Remove(ss);
     context.SaveChanges();
 }