public Repository()
{
_db = new QLBanHangDbContext();
}
// Phuong thuc khoi tao :
internal ChungLoaiRepository(QLBanHangDbContext db)
{
_db = db;
}
// Phuong thuc khoi tao :
internal HangHoaRepository(QLBanHangDbContext db)
{
_db = db;
}
