public ActionResult AddTheUserToTheCourse(AllUsersAndSomeCourseViewModel model)
        {
            if (ModelState.IsValid)
            {
                using (_db)
                {
                    var    newConnection = _db.userCourse.Create();
                    string theUserId     = model.SelectedUserId;

                    newConnection.userId = theUserId;
                    if (theUserId.IsNullOrWhiteSpace())
                    {
                        return(Redirect("/Course/AddToCourse/" + model.TheCourse.Id));
                    }

                    var allUsersInCourse = _courseService.GetUsersInSomeCourse(model.TheCourse.Id);
                    foreach (var user in allUsersInCourse)
                    {
                        //Check if user is already in the course
                        if (theUserId == user.userId)
                        {
                            return(Redirect("/Course/AddToCourse/" + model.TheCourse.Id));
                        }
                    }
                    newConnection.userId   = theUserId;
                    newConnection.courseId = model.TheCourse.Id;
                    _db.userCourse.Add(newConnection);
                    _db.SaveChanges();
                }
            }
            //Redirect back to the same page
            return(Redirect("/Course/AddToCourse/" + model.TheCourse.Id));
        }
        public ActionResult AddToCourse(int?id)
        {
            int realId;

            if (id != null)
            {
                realId = (int)id;
            }
            else
            {
                throw new ArgumentNullException();
            }
            AllUsersAndSomeCourseViewModel allUsersAndSomeCourseViewModel = new AllUsersAndSomeCourseViewModel()
            {
                TheCourse        = _courseService.GetCourseById(realId),
                ListOfUsers      = _db.Users.ToList(),
                AllUsersInCourse = _courseService.GetUsersInSomeCourse(realId)
            };

            return(View(allUsersAndSomeCourseViewModel));
        }