public ActionResult Edit(AbsenceViewModel viewModel)
        {
            if (ModelState.IsValid)
            {
                var absence = db.Absences.FirstOrDefault(a => a.Id == viewModel.Id);

                absence.AbsenceDate = viewModel.AbsenceDate;
                absence.CourseTitle = viewModel.CourseTitle;
                absence.StudentFirstName = viewModel.StudentFirstName;
                absence.StudentLastName = viewModel.StudentLastName;
                absence.CourseId = viewModel.CourseId;
                absence.StudentId = viewModel.StudentId;

                db.SaveChanges();

                return RedirectToAction("Index");
            }
            return View(viewModel);
        }
        // GET: Absence/Edit/5
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }
            Absence absence = db.Absences.Find(id);
            if (absence == null)
            {
                return HttpNotFound();
            }

            var viewModel = new AbsenceViewModel();

            viewModel.AbsenceDate = absence.AbsenceDate.Date;
            viewModel.CourseTitle = absence.CourseTitle;
            viewModel.StudentFirstName = absence.StudentFirstName;
            viewModel.StudentLastName = absence.StudentLastName;
            viewModel.Id = absence.Id;
            viewModel.CourseId = absence.CourseId;
            viewModel.StudentId = absence.StudentId;

            return View(viewModel);
        }