QR Code Generation and Verification

In this blog post you will learn all about QR Code, starting from requirement to generation to verification. I am going to develop this in C# and in ASP.NET Web Forms, but you can use it with MVC, Desktop Apps etc. I will be using MessagingToolkit.QRCode open source library for everything here.

Requirement

Let’s assume we have a requirement to print QR Code on certificates. The purpose of this QR Code on certificate is to validate/verify it anytime by anybody. You can restrict the verification if you want but I’m going to develop so that anyone can scan QR Code printed on the certificate and check details of the certificate. This way certificate fraud print will not be possible and easily be recognized.

If this make sense, let’s develop this.

Generating QR Code

Generating this is pretty simple, let’s follow the steps to generate QR Codes.

Step 1: Create a project, I’ll create simple ASP.NET Web Forms project.

Step 2: Install MessagingToolkit.QRCode NuGet package.

Step 3: Define hosting URI and randomly generate QR Code file name, as give below:

string domain = "http://localhost:2779/";

string qrCodeImgFileName = new Random().Next().ToString() + ".jpg";

Step 4: Generate message to be printed on QR Code, I’ll be printing QR Code file URI itself on the QR Code, you can customize/update according to your need later on.

string qrCodeInformation = domain + "ValidateQR.aspx?identity=" + qrCodeImgFileName;

QRCodeEncoder qe = new QRCodeEncoder();

System.Drawing.Bitmap bm = qe.Encode(qrCodeInformation);

Step 5: Once you have QR Code bits as Bitmap, go ahead and save QR Code bitmap into memory stream and save memory stream into file.

// Save QR Code bitmap to memory stream

var memStream = new MemoryStream();

bm.Save(memStream, System.Drawing.Imaging.ImageFormat.Jpeg);

// Save Jpeg stream into file

using (var fileStream = new FileStream(Server.MapPath("~/QRCodes/") + qrCodeImgFileName, FileMode.CreateNew, FileAccess.ReadWrite))

{

    memStream.Position = 0;

    memStream.CopyTo(fileStream);

}

Step 6: If you run your project here, you will see a file gets created inside QRCodes folder on the root. But let’s take this one step ahead and display this on the same web page just after QR Code generation.

Image1.ImageUrl = "~/QRCodes/" + qrCodeImgFileName;

Label1.Text = qrCodeInformation;

Here is the output of the generated QR Code and the URI you see below in the image is the information printed on the QR Code. So, if you scan this image right now, you will see that URI.

That’s all you need to generate QR Code. Now, let’s implement its verification system.

Verification of QR Code

In order to verify the QR Code, one will scan this from device, that device will decode the QR and display that message. In my case that message is URI in the image above.

If you scan above QR Code using https://webqr.com/, you will see following option to navigate. Notice the URI is exact same here as well.

Let’s recall our context here again, student is provided a certificate with QR Code and one will scan that and navigate to verification website.

Now, either we need a logic to read the URI and provide full details of that certificate from our certificate database. Or, we feed up the QR Code file to MessagingToolkit.QRCode and this will decode information, in our case that information is nothing but complete URI.

For the sake of this demo, I’ll just test if that QR Code file is exist or not. Here’s the code, which will execute on page load.

protected void Page_Load(object sender, EventArgs e)

{

    if (Request.QueryString["identity"] != null)

    {

        string qrCodeFileName = Server.MapPath("~/QRCodes/") + Request.QueryString["identity"];

        // Check QR Code file available

        if(File.Exists(qrCodeFileName))

        {

            imgQRCode.ImageUrl = "~/QRCodes/" + Request.QueryString["identity"];

            lblMessage.Text = "QR Code is correct and found.";

            // TODO: Your database calls

        }

        else

        {

            lblMessage.Text = "QR Code not found or invalid.";

        }               

    }

    else

    {

        Response.Redirect("~/GenerateQR.aspx");

    }

}

Notice, I’m reading query string identity and if its available, generating QR Code full file URI and then checking its existence in file system. And if file is available, QR Code will be displayed again with a message QR Code is correct and found. If QR Code file is not available, this will display a message QR Code not found or invalid.

I published the codes on GitHub, you can try that out.

Hope this helps.