asp.net生成验证码

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;using System.Drawing;public partial class AJAX_RandomJpgSam : System.Web.UI.Page{    /// <summary>    /// 生成验证码图片    /// </summary>    /// <param name="checkCode"></param>    private void CreateCheckCodeImage(string checkCode)    {        if (checkCode == null || checkCode.Trim() == String.Empty)            return;        System.Drawing.Bitmap image = newSystem.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 = newSystem.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);            Response.ClearContent();            Response.ContentType = "image/Gif";            Response.BinaryWrite(ms.ToArray());        }        finally        {            g.Dispose();            image.Dispose();        }    }    protected void Page_Load(object sender, EventArgs e)    {        if (Session["CheckCode"] == null)            Session["CheckCode"] = "";        CreateCheckCodeImage(GenerateCheckCode());    }    /// <summary>    /// 客户端验证用户输入验证码    /// </summary>    /// <param name="checkCode"></param>    /// <returns></returns>    public static bool CheckCode(string checkCode)    {        string txt = System.Web.HttpContext.Current.Session["CheckCode"] as string;        return checkCode == txt;    }    /// <summary>    /// 产生随机数    /// </summary>    /// <returns></returns>    private string GenerateCheckCode()    {        int number;        char code;        string checkCode = String.Empty;        System.Random random = new Random();        for (int i = 0; i < 5; i++)        {            number = random.Next();            if (number % 2 == 0)                code = (char)('0' + (char)(number % 10));            else                code = (char)('A' + (char)(number % 26));            checkCode += code.ToString();        }        Session["CheckCode"] = checkCode;        return checkCode;    }}