By default, both Windows Phone 7 and Windows Phone 8 are able to read some types of barcodes using the Bing Vision app. However sometimes you’ll need to read a barcode that Bing Vision does not support, or you’ll want to be able to add barcode functionality into your application. Libraries like this usually support a lot of barcode types and can help you in these tasks.
This article shows how you can add the ability of generating and scanning barcodes using the phone camera to your Windows Phone application. The article illustrates an example application that generates a QR Code containing a phone number you want to share and is able to scan barcodes and display the data stored in them.
Read this article and add barcode generating/scanning functionality to your apps.