How to generate barcode in C# ASP.NET Core
MVC web app?

using Microsoft.AspNetCore.Mvc;
using OnBarcode.QRCodeGenerator.ASPNETCoreMVCDemo.Models;
using System.Diagnostics;

namespace OnBarcode.QRCodeGenerator.ASPNETCoreMVCDemo.Controllers
{
    public class HomeController : Controller
    {
        //  Cannot be empty.
        private static String tbMessage = "QRCode";
        //  Must be a positive float value less than 10.
        private static String tbWidth = "2";
        //  Must be a positive int value less than 1200.
        private static String tbResolution = "300";
        //  Hex String: from 0 to FFFFFF
        private static String tbForeColor = "000000";
        //  Hex String: from 0 to FFFFFF
        private static String tbBackColor = "FFFFFF";

        private readonly ILogger<HomeController> _logger;

        public HomeController(ILogger<HomeController> logger)
        {
            _logger = logger;
        }

        public IActionResult Index()
        {
            //  Set default value to text box.
            ViewData["Message"] = tbMessage;
            ViewData["Width"] = tbWidth;
            ViewData["Resolution"] = tbResolution;
            ViewData["ForeColor"] = tbForeColor;
            ViewData["BackColor"] = tbBackColor;
            return View();
        }

        public IActionResult Privacy()
        {
            return View();
        }

        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        {
            return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
        }

        //  
        public Task<IActionResult> Show()
        {
            try
            {
                //  Update backup 
                tbMessage = Request.Form["tbMessage"].ToString();
                tbWidth = Request.Form["tbWidth"].ToString();
                tbResolution = Request.Form["tbResolution"].ToString();
                tbForeColor = Request.Form["tbForeColor"].ToString();
                tbBackColor = Request.Form["tbBackColor"].ToString();

                byte[] dataBytes = tryToCreateBarcode();
                if (dataBytes == null || dataBytes.Length == 0)
                    throw new Exception("fail to create barcode");
                ViewData["BarcodeImage"] = System.Convert.ToBase64String(dataBytes);

                ViewData["ViewResult"] = "SUCCESS";
                return Task.FromResult<IActionResult>(View());
            }
            catch (Exception)
            {
                //return Task.FromResult<IActionResult>(RedirectToAction(nameof(Index)));
                ViewData["ViewResult"] = "FAILED";
                return Task.FromResult<IActionResult>(View());
            }
        }

        //  Create barcode. Return empty array if failed.
        private byte[] tryToCreateBarcode()
        {
            try
            {
                if (String.IsNullOrEmpty(tbMessage))
                    throw new Exception("Message cannot be null or empty.");
                int resolution = Convert.ToInt32(tbResolution);
                if (resolution > 1200)
                    throw new Exception("Resolution out of range.");
                float width = Convert.ToSingle(tbWidth);
                if (width > 10F)
                    throw new Exception("Width out of range.");
                //  Hex String: RRGGBB
                uint rgbForeColor = Convert.ToUInt32(tbForeColor, 16) & 0xFFFFFF;
                //  Hex String: RRGGBB
                uint rgbBackColor = Convert.ToUInt32(tbBackColor, 16) & 0xFFFFFF;

                OnBarcode.Barcode.QRCode qrcode = new OnBarcode.Barcode.QRCode();
                qrcode.DataMode = Barcode.QRCodeDataMode.Auto;
                qrcode.Data = tbMessage;
                qrcode.UOM = Barcode.UnitOfMeasure.INCH;

                qrcode.Resolution = resolution;
                qrcode.BarcodeWidth = width;
                qrcode.BarcodeHeight = width;
                qrcode.ForeColor = new SkiaSharp.SKColor(0xFF000000 + rgbForeColor);
                qrcode.BackColor = new SkiaSharp.SKColor(0xFF000000 + rgbBackColor);

                qrcode.AutoResize = true;
                qrcode.ImageFormat = SkiaSharp.SKEncodedImageFormat.Png;
                return qrcode.drawBarcodeAsBytes();
            }
            catch (Exception)
            {
                return new byte[0];
            }
        }
    }
}

@{
    ViewData["Title"] = "Home Page";
}

<div class="text-center">
    <br />
    <form asp-action="Show">
        <table align="center">
            <tbody>
                <tr>
                    <td align="right">Data Message: &nbsp;&nbsp;</td>
                    <td>
                        <input type="text" id="tb1" name="tbMessage" style="width: 300px; " asp-for=@ViewData["Message"] />
                    </td>
                </tr>
                <tr>
                    <td align="right">Width (inch): &nbsp;&nbsp;</td>
                    <td>
                        <input type="text" id="tb2" name="tbWidth" style="width: 300px; " asp-for=@ViewData["Width"] />
                    </td>
                </tr>
                <tr>
                    <td align="right">Resolution (dpi): &nbsp;&nbsp;</td>
                    <td>
                        <input type="text" id="tb3" name="tbResolution" style="width: 300px; " asp-for=@ViewData["Resolution"] />
                    </td>
                </tr>
                <tr>
                    <td align="right">Fore Color: &nbsp;&nbsp;</td>
                    <td>
                        <input type="text" id="tb4" name="tbForeColor" style="width: 300px; " asp-for=@ViewData["ForeColor"] />
                    </td>
                </tr>
                <tr>
                    <td align="right">Back Color: &nbsp;&nbsp;</td>
                    <td>
                        <input type="text" id="tb5" name="tbBackColor" style="width: 300px; " asp-for=@ViewData["BackColor"] />
                    </td>
                </tr>
            </tbody>
        </table>
        <br />
        <input type="submit" value="Show" />
        <br />
        <br />
    </form>
</div>