一个用于生成验证码的C#类代码

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',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),new Font(new FontFamily("Arial"),new Font(new FontFamily("Comic Sans MS"),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)));
            }
            image = TwistImage(image,true,Next(1,3),Next(4,6));
            g.DrawRectangle(new Pen(Color.LightGray,1),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_Sencond = new Random((int)DateTime.Now.Ticks);
            int int_Red = RandomNum_First.Next(180);
            int int_Green = RandomNum_Sencond.Next(180);
            int int_Blue = (int_Red + int_Green > 300) ? 0 : 400 - int_Red - int_Green;
            int_Blue = (int_Blue > 255) ? 255 : int_Blue;
            return Color.FromArgb(int_Red,int_Green,int_Blue);
        }
 
        /// <summary>
        /// 正弦曲线Wave扭曲图片
        /// </summary>
        /// <param name="srcBmp">图片路径</param>
        /// <param name="bXDir">如果扭曲则选择为True</param>
        /// <param name="nMultValue">波形的幅度倍数，越大扭曲的程度越高,一般为3</param>
        /// <param name="dPhase">波形的起始相位,取值区间[0-2*PI)</param>
        public System.Drawing.Bitmap TwistImage(Bitmap srcBmp,bool bXDir,double dMultValue,double dPhase)
        {
            double PI = 6.283185307179586476925286766559;
            Bitmap destBmp = new Bitmap(srcBmp.Width,srcBmp.Height);
            Graphics graph = Graphics.FromImage(destBmp);
            graph.FillRectangle(new SolidBrush(Color.White),destBmp.Width,destBmp.Height);
            graph.Dispose();
            double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
            for (int i = 0; i < destBmp.Width; i++)
            {
                for (int j = 0; j < destBmp.Height; j++)
                {
                    double dx = 0;
                    dx = bXDir ? (PI * (double)j) / dBaseAxisLen : (PI * (double)i) / dBaseAxisLen;
                    dx += dPhase;
                    double dy = Math.Sin(dx);
                    int nOldX = 0,nOldY = 0;
                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);
 
                    Color color = srcBmp.GetPixel(i,j);
                    if (nOldX >= 0 && nOldX < destBmp.Width
                     && nOldY >= 0 && nOldY < destBmp.Height)
                    {
                        destBmp.SetPixel(nOldX,nOldY,color);
                    }
                }
            }
            srcBmp.Dispose();
            return destBmp;
        }
        #endregion
    }
}