asp.net随机验证码（使用ashx）

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ValidateCode.ashx

<%@ WebHandler Language="C#" Class="ValidateCode" %>
using System;
using System.Data;
using System.Web;
using System.Collections;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Drawing;

public class ValidateCode : IHttpHandler
{

        public void ProcessRequest(HttpContext context)
        {
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);//特别注意，如不加，单击验证图片＇看不清换一张＇，无效果．
            this.CreateCheckCodeImage(GenerateCheckCode(context),context);
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
        private string GenerateCheckCode(HttpContext context)
        {
            int number;
            char code;
            string checkCode = String.Empty;

System.Random random = new Random();

            for (int i = 0; i < 6; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else if (number % 3 == 0)
                    code = (char)('A' + (char)(number % 26));
                else
                    code = (char)('a' + (char)(number % 26));
                checkCode += code.ToString();
            }

            context.Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//也可以存到Seesion里．
            //context.Session["CheckCode"] = checkCode;

            return checkCode;
        }

        private void CreateCheckCodeImage(string checkCode, HttpContext context)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return;

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);

                //画图片的背景噪音线
                for (int i = 0; i < 25; i++)
                {
                    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.Silver), x1, y1, x2, y2);
}

                Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
                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);

                //画图片的前景噪音点
                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()));
}

//画图片的边框线
g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                context.Response.ClearContent();
                context.Response.ContentType = "image/Gif";
                context.Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }

}
}

页面:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

后台代码:

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

}

        protected void Button1_Click(object sender, EventArgs e)
        {
            if (Request.Cookies["CheckCode"] == null)
            {
                lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";
                lblMessage.Visible = true;
                return;
            }

            if (String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)
            {
                lblMessage.Text = "验证码错误，请输入正确的验证码。";
                lblMessage.Visible = true;
                return;
            }
        　 //在这执行下一步


            //CheckCode是存到Session里的
            //if (Session["CheckCode"] != null)
            //{
            //    if (String.Compare(Session["CheckCode"].ToString(), txtCheckCode.Text.Trim(), true) != 0)
            //    {
            //        lblMessage.Text = "验证码错误，请输入正确的验证码。";
            //        lblMessage.Visible = true;
            //        return;
            //    }
            //    else
            //    {//在这执行下一步
            //    }
            //}
        }
    }