//// <summary>

        /// 生成验证码

        /// </summary>

        /// <param name="length">指定验证码的长度</param>

        /// <returns></returns>

        public string CreateValidateCode(int length)

        {

            int[] randMembers = new int[length];

            int[] validateNums = new int[length];

            string validateNumberStr = "";

            //生成起始序列值

            int seekSeek = unchecked((int)DateTime.Now.Ticks);

            Random seekRand = new Random(seekSeek);

            int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);

            int[] seeks = new int[length];

            for (int i = 0; i < length; i++)

            {

                beginSeek += 10000;

                seeks[i] = beginSeek;

            }

            //生成随机数字

            for (int i = 0; i < length; i++)

            {

                Random rand = new Random(seeks[i]);

                int pownum = 1 * (int)Math.Pow(10, length);

                randMembers[i] = rand.Next(pownum, Int32.MaxValue);

            }

            //抽取随机数字

            for (int i = 0; i < length; i++)

            {

                string numStr = randMembers[i].ToString();

                int numLength = numStr.Length;

                Random rand = new Random();

                int numPosition = rand.Next(0, numLength - 1);

                validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));

            }

            //生成验证码

            for (int i = 0; i < length; i++)

            {

                validateNumberStr += validateNums[i].ToString();

            }

            return validateNumberStr;

        }

/// <summary>

/// 创建验证码的图片

/// </summary>

/// <param name="containsPage">要输出到的page对象</param>

/// <param name="validateNum">验证码</param>

public byte[] CreateValidateGraphic(string validateCode)

{

    Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 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);

        //画图片的干扰线

        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 Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));

        LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),

         Color.Blue, Color.DarkRed, 1.2f, true);

        g.DrawString(validateCode, font, brush, 3, 2);

        //画图片的前景干扰点

        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);

        //保存图片数据

        MemoryStream stream = new MemoryStream();

        image.Save(stream, ImageFormat.Jpeg);

        //输出图片流

        return stream.ToArray();

    }

    finally

    {

        g.Dispose();

        image.Dispose();

    }

}

public ActionResult GetValidateCode()

    {

        ValidateCode vCode = new ValidateCode();

        string code = vCode.CreateValidateCode(5);

        Session["ValidateCode"] = code;

        byte[] bytes = vCode.CreateValidateGraphic(code);

        return File(bytes, @"image/jpeg");

    }  

<p>

<img id="valiCode" style="cursor: pointer;" src="/Home/GetValidateCode" alt="验证码" />

</p>  

<script>

    $(function () {

        $("#valiCode").bind("click", function () {

            this.src = "/Home/GetValidateCode?time=" + (new Date()).getTime();

        });

    });</script>