Reading QR Codes in Unity

I’m currently working on a project reading QR codes with the Microsoft Hololens (UWP). I’m developing the application in Unity (5.4.0 build 24) in C# and I’m using ZXing to read the QR codes. I downloaded ZXing from this webpage and I ended up using the .NET 3.5 version. I was able to generate a byte array corresponding to the view of the Hololens. I then want to use the decode function to get the text in the QR code:

ZXing.Result result = reader.Decode(img_bitmap);

However, in order to use this, I need to create a Bitmap, which is included in System.Drawing. As I understand, Unity3D doesn’t include this package, so I followed the instructions in this answer and included System.Drawing from .NET 2.0. However, when I try to build, I get the following error:

error CS7069: Reference to type 'MarshalByRefObject' claims it is defined in 'mscorlib', but it could not be found.

According to my understanding, Unity builds to something close to .NET 3.5, but I’ve been unable to find a .NET 3.5 version of System.Drawing on my system (and I’m not convinced this is the root of the problem anyway). Any ideas? Thanks in advance!

Cross platform QR code scanner and generator for unity 3d is available on assets store, check this blog it may help you.