//button点击事件
private void button1_Click(object sender, EventArgs e)
{
  if (string.IsNullOrEmpty(textBox1.Text))
  {
   MessageBox.Show("请输入要生成的二维码！");
   return;
  }
  GenByZXingNet(textBox1.Text);
}

//生成二维码图片的函数
private Bitmap GenByZXingNet(string msg)
 {
  BarcodeWriter writer = new BarcodeWriter();
  writer.Format = BarcodeFormat.QR_CODE;
  writer.Options.Hints.Add(EncodeHintType.CHARACTER_SET, "UTF-8");//编码问题
  writer.Options.Hints.Add(EncodeHintType.ERROR_CORRECTION, ZXing.QrCode.Internal.ErrorCorrectionLevel.H);
  const int codeSizeInPixels = 240; //设置图片长宽
  writer.Options.Height = writer.Options.Width = codeSizeInPixels;
  writer.Options.Margin = 1;//设置边框
  ZXing.Common.BitMatrix bm = writer.Encode(msg);
  Bitmap img = writer.Write(bm);
  pictureBox1.Image = img;
  return img;
 }

//若需要打开exe默认出现一张二维码，先给textbox初始值，然后添加函数
private void Form1_Load(object sender, EventArgs e)
 {
  button1_Click(null,null);
 }