public frm_TraSach() { InitializeComponent(); phieuPhatDTO = new PhieuPhat_DTO(); phieuPhatBUS = new PhieuPhat_BUS(); phieuTraBUS = new PhieuTra_BUS(); phieuTraDTO = new PhieuTra_DTO(); ctTraSachBUS = new ChiTietTraSach_BUS(); ctTraSachDTO = new ChiTietTraSach_DTO(); }