Barcode Reader control for Windows Phone 8 is a ready to use XAML control that allow you to read barcodes and QR codes.
This control is an implementation of Zxing.net.

In order to use the control install it via nuget. PM> Install-Package FM.Barcode

Then include the following namespace in your XAML file. xmlns:fm="clr-namespace:FM.Barcode;assembly=FM.Barcode"

Once done you can use the scanner control in your page <fm:ScannerControl x:Name="ScanControl" />

In order to support app switching please insert the following code in the method Application_Activated located in your App.xaml.cs

private void Application_Activated(object sender, ActivatedEventArgs e)
{  
    FM.Barcode.ScannerControl.ReloadComponents();  
}