/// <summary>
        /// lấy danh sách chi tiết trả nợ của khách hàng cho 1 khoản nợ nào đó
        /// </summary>
        /// <param name="pMaHoaDon">mã hóa đơn nợ</param>
        /// <returns>danh sách chi tiết phiểu trả nợ</returns>
        public List <eChiTietPhieuTraNoKhachHang> GetListChiTietTraNoKH(string pMaHoaDon)
        {
            List <eChiTietPhieuTraNoKhachHang> l = new List <eChiTietPhieuTraNoKhachHang>();

            foreach (var ct in db.ChiTietPhieuTraNoKhachHangs.Where(e => e.MaHoaDonBanSi == pMaHoaDon))
            {
                eChiTietPhieuTraNoKhachHang ect = new eChiTietPhieuTraNoKhachHang();

                ect.SoTien                = ct.SoTien;
                ect.GhiChu                = ct.GhiChu;
                ect.MaHoaDonBanSi         = ct.MaHoaDonBanSi;
                ect.MaChiTietPhieuTraNoKH = ct.MaChiTietPhieuTraNoKH;
                ect.MaNhanVien            = ct.MaNhanVien;
                ect.NgayTra               = ct.NgayTra;
                l.Add(ect);
            }
            return(l);
        }
        public eChiTietPhieuTraNoKhachHang ThuNoKH(string pMaHoaDonBanSi, string pMaNhanVien, decimal pSoTien, string pGhiChu)
        {
            KiemTraTraNoKH(pMaHoaDonBanSi, pSoTien);
            ChiTietPhieuTraNoKhachHang  ct  = new ChiTietPhieuTraNoKhachHang();
            eChiTietPhieuTraNoKhachHang ect = new eChiTietPhieuTraNoKhachHang();

            ct.MaChiTietPhieuTraNoKH = ect.MaChiTietPhieuTraNoKH = TaoMaChiTietPhieuTraNoKH();
            ct.SoTien        = ect.SoTien = pSoTien;
            ct.MaNhanVien    = ect.MaNhanVien = pMaNhanVien;
            ct.NgayTra       = ect.NgayTra = DateTime.Now;
            ct.MaHoaDonBanSi = ect.MaHoaDonBanSi = pMaHoaDonBanSi;
            ct.GhiChu        = ect.GhiChu = pGhiChu;
            try
            {
                db.ChiTietPhieuTraNoKhachHangs.InsertOnSubmit(ct);
                db.SubmitChanges();
                return(ect);
            }
            catch
            {
                return(null);
            }
        }