public static List <SinhVien> getListSinhVien()
        {
            List <SinhVien> list = new SinhVienDbContext().SinhVienDbSet.Select(e => e).ToList();

            for (int i = 0; i < list.Count; i++)
            {
                //SinhVien temp = list.ElementAt(i);
                string msv = list.ElementAt(i).MaSinhVien;
                list.ElementAt(i).ListDiemHocTap = DiemHocTap.getDiemHocTap(msv);
            }
            return(list);
        }
        public static void themDiemHocTap(string maSinhVien, string maMonHoc1, string tenMonHoc1, double diem1, string maMonHoc2, string tenMonHoc2, double diem2)
        {
            var        db          = new SinhVienDbContext();
            DiemHocTap diemHocTap1 = new DiemHocTap {
                MaMonHoc = maMonHoc1, Diem = diem1, MaSinhVien = maSinhVien, TenMonHoc = tenMonHoc1
            };
            DiemHocTap diemHocTap2 = new DiemHocTap {
                MaMonHoc = maMonHoc2, Diem = diem2, MaSinhVien = maSinhVien, TenMonHoc = tenMonHoc2
            };

            db.DiemHocTapDbSet.Add(diemHocTap1);
            db.DiemHocTapDbSet.Add(diemHocTap2);
            db.SaveChanges();
        }