Form1.cs

using System.Diagnostics;
using System.Drawing;
using System.Net;
using ZXing.Windows.Compatibility;

namespace WinFormsAppQRCode
{
    public partial class Form1 : Form
    {
        private readonly HttpClient httpClient = new HttpClient();
        private readonly BarcodeReader barcodeReader = new BarcodeReader();

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Process process = new Process()
            {
                StartInfo = new ProcessStartInfo()
                {
                    UseShellExecute = true,
                    FileName = button1.Text,
                }
            };

            process.Start();
        }

        private void button1_TextChanged(object sender, EventArgs e)
        {
            if (button1.Text.Length > 0)
            {
                button1.Enabled = true;
            }
            else
            {
                button1.Enabled = false;
            }
        }

        
        private void Form1_KeyDown_1(object sender, KeyEventArgs e)
        {
            if (e.Control && e.KeyCode == Keys.V)
            {
                if (Clipboard.ContainsData(DataFormats.Bitmap))
                {
                    pictureBox1.Image = (Bitmap)Clipboard.GetDataObject().GetData(DataFormats.Bitmap);
                    button1.Text = DecodeQRCode(pictureBox1.Image);
                }
            }
        }

        private string DecodeQRCode(Image image)
        {
            return barcodeReader.Decode((Bitmap)image)?.Text ?? string.Empty;
        }

        private async void Form1_DragDrop_1(object sender, DragEventArgs e)
        {
            try
            {
                if (e.Data.GetDataPresent(DataFormats.FileDrop))
                {
                    string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
                    if (files.Length == 1)
                    {
                        pictureBox1.Image = Image.FromFile(files[0]);
                        button1.Text = DecodeQRCode(pictureBox1.Image);
                        return;
                    }
                    else
                    {
                        throw new Exception("Only max 1");
                    }
                }
                else if (e.Data.GetDataPresent(DataFormats.Text))
                {

                    string url = e.Data.GetData(DataFormats.Text).ToString();
                    byte[] imageData = await httpClient.GetByteArrayAsync(url);
                    pictureBox1.Image = Image.FromStream(new MemoryStream(imageData));
                    button1.Text = DecodeQRCode(pictureBox1.Image);
                    return;
                }
                //else if(e.Data.GetDataPresent(DataFormats.Bitmap))
                //{
                //    pictureBox1.Image = (Bitmap)e.Data.GetData(DataFormats.Bitmap);
                //}
                else
                {
                    throw new Exception("Not filedrop or text");
                }
            }
            catch (Exception ex)
            {
                pictureBox1.Image?.Dispose();
                button1.Text = string.Empty;
                MessageBox.Show(ex.ToString());
            }
        }

        private void Form1_DragEnter_1(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.FileDrop) || e.Data.GetDataPresent(DataFormats.Text) 
                || e.Data.GetDataPresent(DataFormats.Bitmap))
            {
                e.Effect = DragDropEffects.Link;
                //copy thì được kéo ảnh ở photo vào.
            }
        }

        private void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            httpClient.Dispose();
        }
    }
}