program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Chapter3._1
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

QRManager.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Drawing;
using QRCoder;

namespace Chapter3._1
{
    class QRManager
    {
        public static void TukarInfo(ref TextBox textBox1, ref TextBox textBox2)
        {
            string temp = textBox1.Text;
            textBox1.Text = textBox2.Text;
            textBox2.Text = temp;
        }

        public static string GenerateInfo(string namaAsal, string alamatAsal, string NoHpAsal, string namaTujuan, string alamatTujuan, string NoHpTujuan)
        {
            string result = "#" + namaAsal + "*" + alamatAsal + "*" + NoHpAsal + "*" + namaTujuan + "*" + alamatTujuan + "*" + NoHpTujuan;
            return result;
        }

        public static string GenerateInfo(string namaAsal, string alamatAsal, string NoHpAsal, string namaTujuan, string alamatTujuan, string NoHpTujuan, out Bitmap QrBitmap)
        {
            string text = GenerateInfo(namaAsal, alamatAsal, NoHpAsal, namaTujuan, alamatTujuan, NoHpTujuan);

            QRCodeGenerator qrGenerator = new QRCodeGenerator();
            QRCodeData qrCodeData = qrGenerator.CreateQrCode(text, QRCodeGenerator.ECCLevel.Q);
            QRCode qrCode = new QRCode(qrCodeData);
            QrBitmap = qrCode.GetGraphic(20);

            return text;
        }
    }
}

Form1.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Chapter3._1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btTukar_Click(object sender, EventArgs e)
        {
            QRManager.TukarInfo(ref tbNamaPenerima, ref tbNamaPengirim);
            QRManager.TukarInfo(ref tbAlamatAsal, ref tbAlamatTujuan);
            QRManager.TukarInfo(ref tbHpPenerima, ref tbHpPengirim);
        }

        private void btProses_Click(object sender, EventArgs e)
        {
            Bitmap qr;
            tbQrText.Text = QRManager.GenerateInfo(
                tbNamaPengirim.Text,
                tbAlamatAsal.Text,
                tbHpPengirim.Text,
                tbNamaPenerima.Text,
                tbAlamatTujuan.Text,
                tbHpPenerima.Text,
                out qr);
            pbQR.BackgroundImage = qr;
        }
    }
}