public void DeleteCourseStudent(string CourseID, string StudentID)
        {
            Console.WriteLine("Izbrisi slusanje slusanje");
            CourseStudent courseStudent = _courseStudentData.Find(StudentID, CourseID);

            _courseStudentData.Delete(courseStudent);
        }
        public IActionResult Activities()
        {
            var             model      = _activityData.FindAll();
            List <Activity> activities = model.ToList();

            for (int i = 0; i < activities.Count; i++)
            {
                Activity      activity      = activities.ElementAt(i);
                CourseStudent courseStudent = _courseStudentData.Find(activity.StudentID, activity.CourseID);

                if (courseStudent.FinalGrade != null)
                {
                    activities.Remove(activity);
                }
            }
            model = activities;
            return(View(model));
        }