public JsonResult GetStudentCourse(string registrationNo)
        {
            List <CourseDetails> courses = aStudentManager.GetStudentCouses();

            var cL = courses.Where(m => m.RegNo == registrationNo).ToList();

            var courseNameList = aStudentManager.GetStudentCourseDetils(cL);

            return(Json(courseNameList));
        }