产生验证码ashx文件

<%@ WebHandler Language="C#" Class="VerifyPic" %>

using System;
using System.Collections;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Xml.Linq;
using System .Web .SessionState ;
using System.IO;
using System.Drawing;

public class VerifyPic : IHttpHandler, IRequiresSessionState
{

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        string temp = GenerateCheckCode();
        context.Session["code"] = temp.ToLower();
        this.CreateCheckCodeImage(temp, context);
    }

    private string GenerateCheckCode()
    {
        string chkCode = string.Empty;
        //颜色列表，用于验证码、噪线、噪点  
        //Color[] color ={ Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };
        //字体列表，用于验证码  
        string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
        //验证码的字符集，去掉了一些容易混淆的字符  
        char[] character = { '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };
        Random rnd = new Random();
        //生成验证码字符串  
        for (int i = 0; i < 4; i++)
        {
            chkCode += character[rnd.Next(character.Length)];
        }

        return chkCode;
    }

    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 * 15.5)), 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();
        }
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}