ZXing ExpandedProductParsedResult Throws Null Reference Exception in Xamarin Forms

Question

I'm writing a barcode scanner app in Xamarin Forms and I'm using the ZXing library to handle barcode scanning and parsing. The following code works perfectly, bringing up an alert when the code is scanned:

OnScanResult += (result) => {
            IsScanning = false;

            var parsedResult = ResultParser.parseResult(result);

            Device.BeginInvokeOnMainThread(() => {
                Navigation.PopAsync();
                DisplayAlert("Barcode Info", parsedResult.DisplayResult, "OK");
            });

However, I want to use the ExpandedProductParsed result type for this method and harvest the productID field, so I tried this:

OnScanResult += (result) => {
            IsScanning = false;

            var productResult = ResultParser.parseResult(result) as ExpandedProductParsedResult;

            Device.BeginInvokeOnMainThread(() => {
                Navigation.PopAsync();
                DisplayAlert("Barcode Info", productResult.ProductID, "OK");
            });
        };

For some reason this parse doesn't work and it ends up throwing a null reference exception. Why does the first instance work but not the second one?

if the cast to ExpandedProductResults fails, productResult will be null — Jason, Sep 27 '17 at 18:28
most likely because the result isn't of type ExpandedProductResults. You can test this using the 'is' operator before attempting the cast — Jason, Sep 27 '17 at 18:40
It turns out what I was trying to do wasn't possible. I thought you could just convert a barcode into a bunch of information using the ZXing library, but it turns out that that isn't part of ZXing does. — user8684984, Sep 27 '17 at 19:12

ZXing ExpandedProductParsedResult Throws Null Reference Exception in Xamarin Forms

0 Answers0