public void deleteAttend(int bookId, int authorId)
{
ThamGia e = db.ThamGias.SingleOrDefault(x => x.MaSach == bookId && x.MaTacGia == authorId);
db.ThamGias.Remove(e);
db.SaveChanges();
}
public void createAttend(ThamGia e)
{
db.ThamGias.Add(e);
db.SaveChanges();
}