What i'm missing in here?

Question

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using MessagingToolkit.QRCode.Codec;

using MessagingToolkit.QRCode.Codec.Data;

using DataMatrix.net;

using OnBarcode.Barcode.WinForms;

namespace WindowsFormsApplication1

{

   public partial class Form1 : Form

   {

      public Form1()

      {

         InitializeComponent();

      }

      private void textBox1_TextChanged(object sender, EventArgs e)

      {

      }

      private void button1_Click(object sender, EventArgs e)

      {

         string url = textBox1.Text;

         DmtxImageEncoder encoder = new DmtxImageEncoder();

         Bitmap qrcode = encoder.EncodeImage(url);

         pictureBox1.Image = qrcode as Image;

      }

      private void pictureBox1_Click(object sender, EventArgs e)

      {

      }

      private void button2_Click(object sender, EventArgs e)

      {

         SaveFileDialog s = new SaveFileDialog();

         s.Filter = "PNG|*.png|JPEG|*.jpg|BMP|*.bmp|GIF|*.gif";

         if (s.ShowDialog() == System.Windows.Forms.DialogResult.OK)

         {

            pictureBox1.Image.Save(s.FileName);

         }

      }

      private void button3_Click(object sender, EventArgs e)

      {

         OpenFileDialog o = new OpenFileDialog();

         if (o.ShowDialog() == System.Windows.Forms.DialogResult.OK)

         {

            pictureBox1.ImageLocation = o.FileName;

         }

      }

      

      private void button4_Click(object sender, EventArgs e)

      {

          DmtxImageDecoder decoder = new DmtxImageDecoder();

          //MessageBox.Show(decoder.decode(new QRCodeBitmapImage(pictureBox1.Image as Bitmap)));

      }

   }

}