public ActionResult Edit(SemesterEditViewModel model)
        {
            var semester = Db.Semesters.SingleOrDefault(s => s.Id == model.SemesterId);

            semester.Name         = model.Name;
            semester.StartCourses = DateTime.Parse(model.StartCourses);
            semester.EndCourses   = DateTime.Parse(model.EndCourses);

            Db.SaveChanges();


            return(RedirectToAction("Details", new { id = semester.Id }));
        }
        /// <summary>
        /// Semester verändern
        /// </summary>
        /// <param name="id">SemesterId</param>
        /// <returns></returns>
        public ActionResult Edit(Guid id)
        {
            var model = new SemesterEditViewModel();

            var semester = Db.Semesters.SingleOrDefault(s => s.Id == id);

            model.SemesterId   = semester.Id;
            model.Name         = semester.Name;
            model.StartCourses = semester.StartCourses.ToShortDateString();
            model.EndCourses   = semester.EndCourses.ToShortDateString();


            return(View(model));
        }