public ActionResult Index(string search="")
        {
            StudentIndexViewModel sivm = new StudentIndexViewModel
            {
                Students = studentsRepository.All.ToList(),
                CompetencyHeaders = competencyHeadersRepository.All.ToList()
            };

            return View(sivm);
        }
        public ActionResult Index(string searchString = "")
        {
            IEnumerable<Student> students = _studentsRepository.All;

            if (!string.IsNullOrEmpty(searchString) && searchString.Contains(" "))
            {
                int spaceIndex = searchString.IndexOf(" ");
                int toLastIndex = searchString.Length - spaceIndex;
                var substring1 = searchString.Substring(0, spaceIndex);
                var substring2 = searchString.Substring(spaceIndex + 1, toLastIndex - 1);
                students = _studentsRepository.All.Where(s => s.Firstname == (substring1) && s.Lastname == (substring2));
            }
            else if (!string.IsNullOrEmpty(searchString))
            {
                students = _studentsRepository.All.Where(s => s.Firstname.Contains(searchString) || s.Lastname.Contains(searchString)).OrderBy(x => x.Lastname);
            }

            StudentIndexViewModel viewModel = new StudentIndexViewModel
            {
                Students = students.ToList(),
                CompetencyHeaders = _competencyHeadersRepository.All.ToList()
            };

            return View(viewModel);
        }