C#动态验证码

验证码定义：

就是将一串随机产生的数字或符号，生成一幅图片，图片里加上一些干扰象素（防止OCR），由用户肉眼识别其中的验证码信息，输入表单提交网站验证，验证成功后才能使用某项功能

项目中，我们登录注册都会用到验证码，那为什么我们要使用验证码呢？

经过资料查询以及个人理解，验证码的作用：防止批量进行一些操作：例如贴吧，论坛中匿名发帖，针对某特定用户用特殊破解方式登录尝试，防止机器恶意注册等

在C#中，代码如下：

　　　　　　 try
        　　    {
                Response.Cache.SetCacheability(HttpCacheability.NoCache);
                string randomcode = Globals.CreateVerifyCode(4);

                // 随机转动角度
                int randAngle = 45;
                int mapwidth = (int)(randomcode.Length * 33);
                // 创建图片背景
                Bitmap map = new Bitmap(mapwidth-5, 45);
                Graphics graph = Graphics.FromImage(map);
                // 清除画面，填充背景
                graph.Clear(Color.AliceBlue);
                // 画一个边框
                //graph.DrawRectangle(new Pen(Color.Gray, 0), 0, 0, map.Width-1, map.Height - 3);
                //graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式

                Random rand = new Random();

                // 背景噪点生成
                Pen blackPen = new Pen(Color.LightGray, 0);
                for (int i = 0; i < 50; i++)
                {
                    int x = rand.Next(0, map.Width);
                    int y = rand.Next(0, map.Height);
                    graph.DrawRectangle(blackPen, x, y, 1, 1);
                }

                // 验证码旋转，防止机器识别
                // 拆散字符串成单字符数组
                char[] chars = randomcode.ToCharArray();

                // 文字距中
                StringFormat format = new StringFormat(StringFormatFlags.NoClip);
                format.Alignment = StringAlignment.Center;
                format.LineAlignment = StringAlignment.Center;

                // 定义颜色
                Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Brown, Color.DarkCyan, Color.Purple,Color.DarkGreen };
                // 定义字体
                //string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial","Lucida Sans Unicode", Rockwell, Batang ,Times New Roman,Bernard MT Condensed};

                for (int i = 0; i < chars.Length; i++)
                {
                    int cindex = rand.Next(7);
                    int findex = rand.Next(4);

                    // 字体样式(参数2为字体大小)
                    Font f = new System.Drawing.Font("Microsoft Sans Serif", 17, System.Drawing.FontStyle.Bold);
                    Brush b = new System.Drawing.SolidBrush(c[cindex]);

                    Point dot = new Point(23, 15);
                    // 测试X坐标显示间距的
                    //graph.DrawString(dot.X.ToString(),fontstyle,new SolidBrush(Color.Black),10,150);
                    // 转动的度数
                    float angle = rand.Next(-randAngle, randAngle);

                    // 移动光标到指定位置
                    graph.TranslateTransform(dot.X, dot.Y);
                    graph.RotateTransform(angle);
                    graph.DrawString(chars[i].ToString(), f, b, 1, 10, format);
                    //graph.DrawString(chars[i].ToString(),fontstyle,new SolidBrush(Color.Blue),1,1,format);
                    // 转回去
                    graph.RotateTransform(-angle);
                    // 移动光标到指定位置
                    graph.TranslateTransform(3, -dot.Y);
                }
                // 标准随机码
                //graph.DrawString(randomcode,fontstyle,new SolidBrush(Color.Blue),2,2); 

                // 生成图片
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                map.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

                Response.ClearContent();
                Response.ContentType = "image/gif";
                Response.BinaryWrite(ms.ToArray());

                graph.Dispose();
                map.Dispose();

　　　　　　　　}
　　　　　　　　catch
　　　　　　　　{
　　　　　　　　}

或者我们还有更全的方法实现：

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();
            string result = "";
            System.Random random = new Random();
            for (int i = ; i < Length; i++)
            {
                result += random.Next().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();
            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 = ; i < Length; i++)
            {
                int rnd = random.Next(, 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();
            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 = ; i < Length; i++)
            {
                int rnd = random.Next(, 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 = ;   //验证码位数
        private int letterWidth = ;  //单个字体的宽度范围
        private int letterHeight = ; //单个字体的高度范围
        private static byte[] randb = new byte[];
        private static RNGCryptoServiceProvider rand = new RNGCryptoServiceProvider();
        private Font[] fonts =
    {
       new Font(new FontFamily("Times New Roman"), +Next(),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Georgia"),  + Next(),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Arial"),  + Next(),System.Drawing.FontStyle.Regular),
       new Font(new FontFamily("Comic Sans MS"),  + Next(),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 = ;
            HttpContext.Current.Response.Buffer = true;
            HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-);
            HttpContext.Current.Response.AddHeader("pragma", "no-cache");
            HttpContext.Current.Response.CacheControl = "no-cache";
            this.text = Rand.Number();
            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, );
            value = value % (max + );
            if (value < ) 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 = ; i < ; i++)
            {
                int x1 = Next(image.Width - );
                int x2 = Next(image.Width - );
                int y1 = Next(image.Height - );
                int y2 = Next(image.Height - );
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
            }
            int _x = -, _y = ;
            for (int int_index = ; int_index < this.text.Length; int_index++)
            {
                _x += Next(, );
                _y = Next(-, );
                string str_char = this.text.Substring(int_index, );
                str_char = Next() ==  ? 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 - )], newBrush, thePos);
            }
            for (int i = ; i < ; i++)
            {
                int x = Next(image.Width - );
                int y = Next(image.Height - );
                image.SetPixel(x, y, Color.FromArgb(Next(, ), Next(, ), Next(, )));
            }
            image = TwistImage(image, true, Next(, ), Next(, ));
            g.DrawRectangle(new Pen(Color.LightGray, ), , , int_ImageWidth - , (letterHeight - ));
            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());
            Random RandomNum_Sencond = new Random((int)DateTime.Now.Ticks);
            int int_Red = RandomNum_First.Next();
            int int_Green = RandomNum_Sencond.Next();
            int int_Blue = (int_Red + int_Green > ) ?  :  - int_Red - int_Green;
            int_Blue = (int_Blue > ) ?  : 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 = ; i < destBmp.Width; i++)
            {
                for (int j = ; j < destBmp.Height; j++)
                {
                    double dx = ;
                    dx = bXDir ? (PI * (double)j) / dBaseAxisLen : (PI * (double)i) / dBaseAxisLen;
                    dx += dPhase;
                    double dy = Math.Sin(dx);
                    int nOldX = , nOldY = ;
                    nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                    nOldY = bXDir ? j : j + (int)(dy * dMultValue);  

                    Color color = srcBmp.GetPixel(i, j);
                    if (nOldX >=  && nOldX < destBmp.Width
                     && nOldY >=  && nOldY < destBmp.Height)
                    {
                        destBmp.SetPixel(nOldX, nOldY, color);
                    }
                }
            }
            srcBmp.Dispose();
            return destBmp;
        }
        #endregion
    }
}  

我们将生成的验证码中的字符串存如session或者cookies中，在onclick事件中获取session或者cookies值与用户输入的值进行匹配即可。

 /// <summary>
    ///创建验证码
    /// </summary>
    public class CreateIdentifyingCode
    {
        /// <summary>
        /// 生成随机字符串
        /// </summary>
        /// <param name="codeCount"></param>
        /// <returns></returns>
        public string CreateRandomCode(int codeCount)
        {
            string randomCode = "";
            try
            {
                string allChar = "2,3,4,5,6,7,H,J,K,L,M,N,X,Y,Z,a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,P,Q,R,S,T,U,V,W,r,s,t,u,v,8,9,A,B,C,D,E,F,G,w,x,y,z";
                //按 ,号拆分字符串
                string[] allCharArray = allChar.Split(',');

                int temp = -;
                Random rand = new Random();
                for (int i = ; i < codeCount; i++)
                {
                    if (temp > )
                    {
                        rand = new Random( * temp * ((int)DateTime.Now.Ticks));
                    }
                    int t = rand.Next();
                    if (temp == t)
                    {
                        return CreateRandomCode(codeCount);
                    }
                    temp = t;
                    randomCode += allCharArray[t];
                }
            }
            catch (Exception)
            {

            }

            return randomCode;
        }
        /// <summary>
        /// 创建验证码图片,并保存
        /// </summary>
        /// <param name="validateCode"></param>
        /// <returns></returns>
        public void SaveValidateGraphic(string validateCode, string path)
        {

            byte[] buffer = CreateValidateGraphic(validateCode);
            MemoryStream ms2 = new MemoryStream(buffer, , buffer.Length);
            ms2.Seek(, SeekOrigin.Begin);
            System.Drawing.Image image2 = System.Drawing.Image.FromStream(ms2);
            image2.Save(path + "x.jpg", ImageFormat.Jpeg);
        }
        /// <summary>
        /// 创建验证码图片
        /// </summary>
        /// <param name="validateCode"></param>
        /// <returns></returns>
        public byte[] CreateValidateGraphic(string validateCode)
        {
            //设置图片的宽度与高度
            Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 16.0), );
            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);
                //图片的干扰线
                for (int i = ; i < ; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Width);
                    int y2 = random.Next(image.Width);
                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);

                }
                Font font = new Font("Arial", , (FontStyle.Bold | FontStyle.Italic));
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(validateCode, font, brush, , );
                //画图片的前景干扰点
                for (int i = ; i < ; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);
                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }
                //画图片的干扰线
                g.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );
                //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();
            }

        }
    }

很简单的实用的验证码就介绍到这里，有什么不足的还请大家多多指导。