public class ValidateCode    {        public ValidateCode()        {        }        /// 
        /// 验证码的最大长度        /// 
        public int MaxLength        {            get { return 10; }        }        /// 
        /// 验证码的最小长度        /// 
        public int MinLength        {            get { return 1; }        }        /// 
        /// 生成验证码        /// 
        /// 指定验证码的长度        /// 
            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;        }        /// 
        /// 创建验证码的图片        /// 
        /// 要输出到的page对象        /// 验证码        public byte[] CreateValidateGraphic(string validateCode)        {            Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 15.0), 25);            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", 14, (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();            }        }        /// 
        /// 得到验证码图片的长度        /// 
        /// 验证码的长度        /// 
            public static int GetImageWidth(int validateNumLength)        {            return (int)(validateNumLength * 13.0);        }        /// 
        /// 得到验证码的高度        /// 
        /// 
            public static double GetImageHeight()        {            return 25.5;        }    } 来源于博友