private void LoadTheLoai()
        {
            List <THELOAI> theloais = SachBUS.GetTheLoais();

            cbbTheLoai.DataSource    = theloais;
            cbbTheLoai.DisplayMember = "TenTheLoai";
        }
        private void LoadTheLoai()
        {
            List <THELOAI> theloais = SachBUS.GetTheLoais();

            theloais.ForEach(theloai => cbbTheLoai.Items.Add(((THELOAI)theloai).TenTheLoai));
        }