public ActionResult courses(string search)
        {
            if (search != null)
            {
                return(View(CourseBL.GetByCode(search)));
            }

            else
            {
                return(View(CourseBL.GetAll()));
            }
        }
        public ActionResult Course(string search)
        {
            ModelState.Remove("ID");
            if (search != null)
            {
                return(View(CourseBL.GetByCode(search)));
            }

            else
            {
                return(View(CourseBL.GetAll()));
            }
        }