public ActionResult CreateTraineeAssign(int id)
        {
            var traineeNotInCourse          = _context.Trainees.Where(c => c.CourseId == null).ToList();
            var trainerandtraineecourselist = new TrainersTraineesCourseViewModel()
            {
                Trainees = traineeNotInCourse,
                Course   = _context.Courses.SingleOrDefault(c => c.Id == id)
            };

            return(View(trainerandtraineecourselist));
        }
        public ActionResult Index(int id)
        {
            var trainerInCourse             = _context.Trainers.Where(c => c.CourseId == id).ToList();
            var traineeInCourse             = _context.Trainees.Where(c => c.CourseId == id).ToList();
            var trainerandtraineecourselist = new TrainersTraineesCourseViewModel
            {
                Trainers = trainerInCourse,
                Trainees = traineeInCourse,
                Course   = _context.Courses.SingleOrDefault(c => c.Id == id)
            };

            return(View(trainerandtraineecourselist));
        }