public ActionResult Create(CourseInstructorViewModel courseModel)
        {
            if (ModelState.IsValid)
            {
                var course = courseModel.Course;
                _courseRepository.Create(course);
                _courseRepository.SaveChanges();
                return RedirectToAction("Index");
            } else {

                return View();
            }
        }
        //
        // GET: /Course/Edit/5
        public ActionResult Edit(int id)
        {
            var course = _courseRepository.CourseAndInstructorByCourseId(id);

            var viewModel =//Convert retrieved course from db
                new CourseInstructorViewModel(course);

             return View(viewModel);
        }
        //
        // GET: /Course/Details/5
        public ViewResult Details(int id)
        {
            var course = _courseRepository.CourseAndInstructorByCourseId(id);

            var viewModel = new CourseInstructorViewModel(course);

            return View(viewModel);
        }
 //
 // GET: /Course/Delete/5
 public ActionResult Delete(int id)
 {
     var viewModel = new CourseInstructorViewModel(_courseRepository.CourseAndInstructorByCourseId(id));
     return View(viewModel);
 }
        //
        // GET: /Course/Create
        public ActionResult Create(int id)
        {
            var viewModel = new CourseInstructorViewModel(id);

            return View(viewModel);
        }