原文地址：http://blog.csdn.net/zlfxy/article/details/873333using System;

using System.Collections.Generic;using System.Linq;using System.Text.RegularExpressions;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Text;using ThoughtWorks;using ThoughtWorks.QRCode.Codec.Util;using ThoughtWorks.QRCode.Codec;using ThoughtWorks.QRCode.Codec.Data;using System.Drawing.Imaging;using System.IO;namespace WebTest{    public partial class main : System.Web.UI.Page    {        protected void Page_Load(object sender, EventArgs e)        {        }        protected void Button1_Click(object sender, EventArgs e)        {            QRCodeEncoder qrCodeEncoder = new QRCodeEncoder();            qrCodeEncoder.QRCodeEncodeMode = QRCodeEncoder.ENCODE_MODE.BYTE;            qrCodeEncoder.QRCodeScale = 4;            qrCodeEncoder.QRCodeVersion = 8;            qrCodeEncoder.QRCodeErrorCorrect = QRCodeEncoder.ERROR_CORRECTION.M;            //String data = "Hello 二维码！";              String data = TextBox1.Text.ToString();                        System.Drawing.Bitmap image = qrCodeEncoder.Encode(data);            System.IO.MemoryStream MStream = new System.IO.MemoryStream();            image.Save(MStream, System.Drawing.Imaging.ImageFormat.Png); ///如果生成二维码后，不需要跳转页面，可以将他们注释掉            Response.ClearContent();            Response.ContentType = "image/Png";            Response.BinaryWrite(MStream.ToArray()); //如果生成二维码后，不需要跳转页面，可以将他们注释掉//            //FileInfo f = new FileInfo(@"d:\zl.png");              Directory.CreateDirectory("d:\\zlf");            FileStream fs = new FileStream("d:\\zlf\\zz.png", FileMode.CreateNew, FileAccess.ReadWrite);            BinaryWriter bw = new BinaryWriter(fs, UTF8Encoding.UTF8);            byte[] by = MStream.ToArray();            for (int i = 0; i < MStream.ToArray().Length; i++)                bw.Write(by[i]);            fs.Close(); 　　　　　　　Response.Write"");//如果不需要向页面给出提示，则可以注释

} } }

在前台直接拉textbox和button。控件的ID不要改。textbox中输入的是二维码对应的文本。

需要在项目中添加引用ThoughtWorks.QRCode.dll（百度云中有！）