DIPBefore.cs

// Cart là module cấp cao
public class Cart
{
    public void Checkout(int orderId, int userId)
    {
        // Database, Logger, EmailSender là module cấp thấy
        Database db = new Database();
        db.Save(orderId);
 
        Logger log = new Logger();
        log.LogInfo("Order has been checkout");
 
        EmailSender es = new EmailSender();
        es.SendEmail(userId);
    }
}