【个人使用.Net类库】（4）验证码类

验证码是现在管理系统常用的一种保护用户帐户信息的一种功能。

验证码可以有效防止某个黑客对某一个特定注册用户用特定程序暴力破解方式进行不断的登录尝试，虽然这可能是我们登录麻烦一点，但是对用户的密码安全来说这个功能还是很有必要，也很重要。但在这里我还是要提醒大家要保护好自己的密码同时尽量使自己的密码复杂度高一点，免得你的账号被人盗用后给自己带来不必要的麻烦。

现在使用的验证码类是苏飞论坛的苏飞所写，本人只是学习和使用而已，验证码类如下所示：

/// <summary>/// 类说明：YZMHelper/// 编 码 人：苏飞/// 联系方式：361983679  /// 更新网站：http://www.sufeinet.com/thread-655-1-1.html/// </summary>using System;using System.Web;using System.Drawing;using System.Security.Cryptography;namespace DotNet.Utilities{    /// <summary>    /// 验证码类    /// </summary>    public class Rand    {        #region 生成随机数字        /// <summary>        /// 生成随机数字        /// </summary>        /// <param name="length">生成长度</param>        public static string Number(int Length)        {            return Number(Length, false);        }        /// <summary>        /// 生成随机数字        /// </summary>        /// <param name="Length">生成长度</param>        /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>        public static string Number(int Length, bool Sleep)        {            if (Sleep) System.Threading.Thread.Sleep(3);            string result = "";            System.Random random = new Random();            for (int i = 0; i < Length; i++)            {                result += random.Next(10).ToString();            }            return result;        }        #endregion        #region 生成随机字母与数字        /// <summary>        /// 生成随机字母与数字        /// </summary>        /// <param name="IntStr">生成长度</param>        public static string Str(int Length)        {            return Str(Length, false);        }        /// <summary>        /// 生成随机字母与数字        /// </summary>        /// <param name="Length">生成长度</param>        /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>        public static string Str(int Length, bool Sleep)        {            if (Sleep) System.Threading.Thread.Sleep(3);            char[] Pattern = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };            string result = "";            int n = Pattern.Length;            System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < Length; i++)            {                int rnd = random.Next(0, n);                result += Pattern[rnd];            }            return result;        }        #endregion        #region 生成随机纯字母随机数        /// <summary>        /// 生成随机纯字母随机数        /// </summary>        /// <param name="IntStr">生成长度</param>        public static string Str_char(int Length)        {            return Str_char(Length, false);        }        /// <summary>        /// 生成随机纯字母随机数        /// </summary>        /// <param name="Length">生成长度</param>        /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>        public static string Str_char(int Length, bool Sleep)        {            if (Sleep) System.Threading.Thread.Sleep(3);            char[] Pattern = new char[] { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };            string result = "";            int n = Pattern.Length;            System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));            for (int i = 0; i < Length; i++)            {                int rnd = random.Next(0, n);                result += Pattern[rnd];            }            return result;        }        #endregion    }    /// <summary>    /// 验证图片类    /// </summary>    public class YZMHelper    {        #region 私有字段        PRivate string text;        private Bitmap image;        private int letterCount = 4;   //验证码位数        private int letterWidth = 16;  //单个字体的宽度范围        private int letterHeight = 20; //单个字体的高度范围        private static byte[] randb = new byte[4];        private static RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider();        private Font[] fonts =     {       new Font(new FontFamily("Times New Roman"),10 +Next(1),System.Drawing.FontStyle.Regular),       new Font(new FontFamily("Georgia"), 10 + Next(1),System.Drawing.FontStyle.Regular),       new Font(new FontFamily("Arial"), 10 + Next(1),System.Drawing.FontStyle.Regular),       new Font(new FontFamily("Comic Sans MS"), 10 + Next(1),System.Drawing.FontStyle.Regular)    };        #endregion        #region 公有属性        /// <summary>        /// 验证码        /// </summary>        public string Text        {            get { return this.text; }        }        /// <summary>        /// 验证码图片        /// </summary>        public Bitmap Image        {            get { return this.image; }        }        #endregion        #region 构造函数        public YZMHelper()        {            HttpContext.Current.Response.Expires = 0;            HttpContext.Current.Response.Buffer = true;            HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);            HttpContext.Current.Response.AddHeader("pragma", "no-cache");            HttpContext.Current.Response.CacheControl = "no-cache";            this.text = Rand.Number(4);            CreateImage();        }        #endregion        #region 私有方法        /// <summary>        /// 获得下一个随机数        /// </summary>        /// <param name="max">最大值</param>        private static int Next(int max)        {            rand.GetBytes(randb);            int value = BitConverter.ToInt32(randb, 0);            value = value % (max + 1);            if (value < 0) value = -value;            return value;        }        /// <summary>        /// 获得下一个随机数        /// </summary>        /// <param name="min">最小值</param>        /// <param name="max">最大值</param>        private static int Next(int min, int max)        {            int value = Next(max - min) + min;            return value;        }        #endregion        #region 公共方法        /// <summary>        /// 绘制验证码        /// </summary>        public void CreateImage()        {            int int_ImageWidth = this.text.Length * letterWidth;            Bitmap image = new Bitmap(int_ImageWidth, letterHeight);            Graphics g = Graphics.FromImage(image);            g.Clear(Color.White);            for (int i = 0; i < 2; i++)            {                int x1 = Next(image.Width - 1);                int x2 = Next(image.Width - 1);                int y1 = Next(image.Height - 1);                int y2 = Next(image.Height - 1);                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);            }            int _x = -12, _y = 0;            for (int int_index = 0; int_index < this.text.Length; int_index++)            {                _x += Next(12, 16);                _y = Next(-2, 2);                string str_char = this.text.Substring(int_index, 1);                str_char = Next(1) == 1 ? str_char.ToLower() : str_char.ToUpper();                Brush newBrush = new SolidBrush(GetRandomColor());                Point thePos = new Point(_x, _y);                g.DrawString(str_char, fonts[Next(fonts.Length - 1)], newBrush, thePos);            }            for (int i = 0; i < 10; i++)            {                int x = Next(image.Width - 1);                int y = Next(image.Height - 1);                image.SetPixel(x, y, Color.FromArgb(Next(0, 255), Next(0, 255), Next(0, 255)));            }            image = TwistImage(image, true, Next(1, 3), Next(4, 6));            g.DrawRectangle(new Pen(Color.LightGray, 1), 0, 0, int_ImageWidth - 1, (letterHeight - 1));            this.image = image;        }        /// <summary>        /// 字体随机颜色        /// </summary>        public Color GetRandomColor()        {            Random RandomNum_First = new Random((int)DateTime.Now.Ticks);            System.Threading.Thread.Sleep(RandomNum_First.Next(50));            Random RandomNum_Se