void XuatSachTheoNhaXuatBan()
 {
     try
     {
         string path = @"\NhaXuatBan.txt";
         listSach.DataSource = null;
         textTotal.Clear();
         NhaXuatBans               = NhaXuatBan.DocDanhSachNhaXuatBanArr(path);
         dsChuyenMuc.DataSource    = null;
         dsChuyenMuc.DisplayMember = "TenNhaXuatBan";
         dsChuyenMuc.ValueMember   = "NhaXuatBanID";
         dsChuyenMuc.DataSource    = NhaXuatBans.ToList();
     } catch (Exception ex)
     {
         throw new Exception(ex.Message);
     }
 }
        public static NhaXuatBan[] DocDanhSachNhaXuatBanArr(string path)
        {
            try
            {
                string[] arr = File.ReadAllLines(path);

                NhaXuatBan[] nxb = new NhaXuatBan[arr.Length];
                for (int i = 0; i < arr.Length; i++)
                {
                    string[] rows = arr[i].Split('|');
                    nxb[i] = new NhaXuatBan {
                        NhaXuatBanID = rows[0], TenNhaXuatBan = rows[1], DiaChi = rows[2], SoDienThoai = rows[3]
                    };
                }
                return(nxb);
            } catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
        }