DependencyService returning values

Hi All,

I have a Xamarin.Forms projects, and I am doing Card.IO stuff.

Now I have a problem with DependencyService returning values, stuck here for the whole day.

Code is here>

In PCL, when Clicking button, PCL using dependencyService to scan the credit card,

void button_Clicked(object sender, EventArgs e)
{

    var result =    DependencyService.Get<ICardIO>().Scan();

}

In iOS project, I can get card number, the code shows as below, but how should I do to get the card number in PCL project?

public CardResult Scan()
{

        var appcontroller = UIApplication.SharedApplication.KeyWindow.RootViewController;

        var paymentDelegate = new MyPaymentDelegate();
        var paymentViewController = new CardIOPaymentViewController(paymentDelegate);

        paymentViewController.CollectCVV = false;
        paymentViewController.CollectExpiry = true;

        appcontroller.PresentViewController(paymentViewController, true, null);

        paymentDelegate.OnScanCompleted += (viewController, cardInfo) =>
        {
            Result = new CardIOResult();
            Result.CardNumber = cardInfo.CardNumber;   //  I can get card number here , but how to return it to the PCL?
        };


        return this.Result;

}

Thanks