string TaoMaLopMoi()
        {
            LopBLL lopbll = new LopBLL();
            string malop  = lopbll.GetMaLopMax();

            string[] list = malop.Split('L');
            malop = "L" + (Int32.Parse(list[1]) + 1);
            return(malop);
        }
        //string tenLop = null;
        //string maKhoiLop = null;
        //string siSo = null;

        public ThemSuaLop()
        {
            InitializeComponent();
            lbTop.Text = "Thêm lớp mới";

            LopBLL lopBll   = new LopBLL();
            string maLopMax = lopBll.GetMaLopMax();

            string[] listtemp = maLopMax.Split('L');
            string   maLop    = listtemp[0];

            tbMaLop.Text = maLop;
        }