C#.NET画验证码与Cookie验证

新建页面Code.aspx 在里面话验证码 后台代码：

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.Drawing;public partial class _Default : System.Web.UI.Page{    protected void Page_Load(object sender, EventArgs e)    {        if (!IsPostBack)        {            CreateCheckCodeImage(GenerateCheckCode());        }    }    // 产生四位随机数的方法    private string GenerateCheckCode()    {        int number;        char code;        //表示字符串为空，次字段为只读        string checkCode = string.Empty;        Random random = new Random();        for (int i = 0; i < 4; i++)        {            number = random.Next();            code = (char)('0' + (char)(number % 10));            checkCode += code.ToString();        }        //将验证码保存到cookie中        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));        return checkCode;    }    private void CreateCheckCodeImage(string checkCode)    {        //当随机数是空的时候或者 去掉空格还是空的时候        if (checkCode == null || checkCode.Trim() == string.Empty)            return;        // 创建位图 4 * 12.5        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);        Graphics g = Graphics.FromImage(image);        try        {            //生成随机生成器            Random random = new Random();            //清空图片背景色            g.Clear(Color.White);            //画图片的毕竟噪音线            for (int i = 0; i < 2; i++)            {                //产生随机的起始坐标和重点坐标                int x1 = random.Next(image.Width);                int x2 = random.Next(image.Width);                int y1 = random.Next(image.Height);                int y2 = random.Next(image.Height);                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);            }            //字体 大小12 加粗            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));            // 线性渐变封装            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);            g.DrawString(checkCode, font, brush, 2, 2);            // 画图片的前景噪点            for (int i = 0; i < 100; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));            }            // 花图片的边框线 矩形            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);            //创建其支持存储区为内存的            System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            // 清楚缓冲区流中的所有内容输出            Response.ClearContent();            // 获取或设置输出流的格式            Response.ContentType = "image/gif";            //将一个二进制字符串 写入输出流   ms.ToArray()将整个流内容写入数组            Response.BinaryWrite(ms.ToArray());        }        finally        {            // 释放资源            g.Dispose();            image.Dispose();        }    }}

展示的页面：

验证码用HTML标签ima表示的 src的路径制定到Code.aspx
当点击图片的时候自动的刷新图片的路径 达到更换验证码的目的.。是通过js刷新img的src的路径实现的
<img id="Img1" alt="看不清，请点击我！" onclick="this.src=this.src+'?'" src="Code.aspx" style="width: 73px; height: 22px" align="left" />

验证页面的后台代码：

    protected void Button1_Click(object sender, EventArgs e)    {        string code = this.txtCode.Text;        //从cookie中取出验证码        HttpCookie cookie = Request.Cookies["CheckCode"];        if (code == cookie.Value.ToString())        {            Response.Write("正确");        }        else        {            Response.Write("错误");        }    }

将验证码保存到cookie中：Response.Cookies.Add(new HttpCookie("CheckCode",checkCode));
从 cookie中取出验证码：HttpCookie cookie = Request.Cookies["CheckCode"];