public void Them_Tai_Khoan(TaiKhoan_MODEL TK1)
        {
            string sql = "INSERT INTO TAI_KHOAN VALUES('" + TK1.MA_NHAN_VIEN1 + "','" + TK1.TEN_TAI_KHOAN1 + "','" + TK1.MAT_KHAU1 + "')";

            K.Thao_Tac_Du_Lieu(sql);
        }
        public void Doi_Mat_Khau(TaiKhoan_MODEL TK1)
        {
            string sql = "UPDATE TAI_KHOAN SET MAT_KHAU=N'" + TK1.MAT_KHAU1 + "' WHERE TEN_TAI_KHOAN =N'" + TK1.TEN_TAI_KHOAN1 + "'";

            K.Thao_Tac_Du_Lieu(sql);
        }