public List<Student> MM_GetStudents()
 {
     using (var context = new MMContext())
     {
         var students = context.Students.Include("Courses").ToList();
         return students;
     }
 }
 public void MM_AddStudentCourse(int stdid,int crsid)
 {
     using (var context = new MMContext())
     {
         var course = context.Courses.FirstOrDefault(x => x.CourseId == crsid);
         context.Students.Include("Courses").FirstOrDefault(x => x.StudentId == stdid).Courses.Add(course);
         context.SaveChanges();
     }
 }