验证码类V1

/// <summary>
    /// 验证码类
    /// </summary>
    public class ValidateCode
    {
        /// <summary>
        /// 验证码的最大长度
        /// </summary>
        public int MaxLength { get { return 10; } }

        /// <summary>
        /// 验证码的最小长度
        /// </summary>
        public int MinLength { get { return 1; } }

        /// <summary>
        /// 生成指定长度的验证码字符串
        /// </summary>
        /// <param name="length"></param>
        /// <returns></returns>
        public string CreateValidateCodeStr(int length)
        { 
            //生成起始序列值
            int seed = unchecked((int)DateTime.Now.Ticks);
            Random seedRandom = new Random(seed);
            int beginSeed = seedRandom.Next(0, Int32.MaxValue - length * 10000);
            int[] seeds=new int[length];
            for (int i = 0; i < length; i++)
            {
                beginSeed += 10000;
                seeds[i] = beginSeed;
            }

            //生成随机数
            int[] randMembers = new int[length];
            for (int i = 0; i < length; i++)
            {
                Random rand = new Random(seeds[i]);
                int p = 1 * (int)Math.Pow(10, length);
                randMembers[i] = rand.Next(p, Int32.MaxValue);
            }

            //抽取随机数字
            int[] validateNums=new int[length];
            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
            string validateCodeStr = "";
            for (int i = 0; i < length; i++)
            {
                validateCodeStr += validateNums[i].ToString();
            }

            return validateCodeStr;
        }

        /// <summary>
        /// 创建验证码的图片
        /// </summary>
        /// <param name="validateCodeStr"></param>
        /// <returns></returns>
        public byte[] CreateValidateImg(string validateCodeStr)
        {
            Bitmap bitmap = new Bitmap((int)Math.Ceiling(validateCodeStr.Length * 12.0), 22);
            Graphics g = Graphics.FromImage(bitmap);
            try
            {
                //清空图片的背景色
                g.Clear(Color.White);
                //实例化随机生成器
                Random rand = new Random();
                //画图片的干扰线
                for (int i = 0; i < 25; i++)
                {
                    int x1 = rand.Next(bitmap.Width);
                    int y1 = rand.Next(bitmap.Height);
                    int x2 = rand.Next(bitmap.Width);
                    int y2 = rand.Next(bitmap.Height);
                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }
                //画字符串
                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, bitmap.Width, bitmap.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(validateCodeStr, font, brush, 3, 2);
                //画图片的前景干扰点
                for (int i = 0; i < 100; i++)
                {
                    int x = rand.Next(bitmap.Width);
                    int y = rand.Next(bitmap.Height);
                    bitmap.SetPixel(x, y, Color.FromArgb(rand.Next()));
                }
                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, bitmap.Width - 1, bitmap.Height - 1);
                //保存图片数据
                MemoryStream stream = new MemoryStream();
                bitmap.Save(stream, ImageFormat.Jpeg);
                //输出图片流
                return stream.ToArray();
            }
            finally 
            {
                g.Dispose();
                bitmap.Dispose();
            }
        }

        /// <summary>
        /// 得到验证码图片的长度
        /// </summary>
        /// <param name="validateNumLength">验证码的长度</param>
        /// <returns></returns>
        public static int GetImgWidth(int validateNumLength)
        {
            return (int)(validateNumLength * 12.0);
        }

        /// <summary>
        /// 得到验证码图片的高度
        /// </summary>
        /// <returns></returns>
        public static double GetImgHeight()
        {
            return 22.5;
        }
    }