public void AddActivity(int StudentId, int?GroupId, int?ClassroomId, TimeSpans TimeSpan, string Place,
                                string Title, string content)
        {
            _context.TimeSpans.Add(TimeSpan);

            Activities act = new Activities
            {
                GroupId         = GroupId,
                TimeSpanId      = TimeSpan.TimeSpanId,
                ClassroomId     = ClassroomId,
                Place           = Place,
                Title           = Title,
                ActivityContent = content,
                Cancelling      = false,
            };

            _context.Activities.Add(act);

            StudentsActivities sa = new StudentsActivities
            {
                StudentId  = StudentId,
                ActivityId = act.ActivityId,
                Ignore     = false,
                Alert      = false
            };

            _context.StudentsActivities.Add(sa);

            _context.SaveChanges();
        }
        public void DeleteActivity(int StudentId, int ActivityId)
        {
            StudentsActivities sa = _context.StudentsActivities.Include(a => a.Activity).First(a => a.StudentId == StudentId && a.ActivityId == ActivityId);
            Activities         ac = sa.Activity;

            _context.Remove(sa);
            _context.Remove(ac);
            _context.SaveChanges();
        }
        public void AlertActivity(int StudentId, int ActivityId)
        {
            StudentsActivities sa = _context.StudentsActivities.First(a => a.StudentId == StudentId && a.ActivityId == ActivityId);

            if (sa.Alert == true)
            {
                throw new Exception("vec je Alertovan");
            }
            sa.Alert = true;
            _context.SaveChanges();
        }