一、验证码简介

一、验证码简介

验证码功能一般是用于防止批量注册的，不少网站为了防止用户利用机器人自动注册、登录、灌水，都采用了验证码技术。所谓验证码，就是将一串随机产生的数字或字母或符号或文字，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。

常见的验证码有如下几种：

1、纯数字验证码，一般为四位随机数字；

2、数字+字母验证码，一般从数字（0~9）和字母(A~Z和a~z)中随机抽出几个字符组成；

3、汉字验证码，相对而言，这种验证码比较少见一点，实现起来也相对复杂一些，但在不少网站中还是可以看到的；

二、验证码的实现

1、纯数字验证码的实现

纯数字验证码的实现相对比较简单，可通过以下两种方法来实现

（1）使用随机数方式，代码如下：

view plaincopy to clipboardprint? private String GetRandomint(int codeCount)    {        Random random = new Random();        string min = "";        string max = "";        for (int i = 0; i < codeCount; i++)        {            min +="1";            max+="9";        }            return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());    }           private String GetRandomint(int codeCount)         {             Random random = new Random();             string min = "";             string max = "";             for (int i = 0; i < codeCount; i++)             {                 min +="1";                 max+="9";             }                 return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());         }

(2)使用随机组合方式，代码如下：

view plaincopy to clipboardprint? private string CreateRandomCode(int codeCount)    {        string allChar = "0,1,2,3,4,5,6,7,8,9";         string[] allCharArray = allChar.Split(',');         string randomCode = "";         int temp = -1;         Random rand = new Random();         for (int i = 0; i < codeCount; i++)         {             if (temp != -1)             {                 rand = new Random(i * temp * ((int)DateTime.Now.Ticks));             }             int t = rand.Next(9);             if (temp == t)             {                 return CreateRandomCode(codeCount);             }             temp = t;             randomCode += allCharArray[t];         }         return randomCode;    }           private string CreateRandomCode(int codeCount)         {             string allChar = "0,1,2,3,4,5,6,7,8,9";              string[] allCharArray = allChar.Split(',');              string randomCode = "";              int temp = -1;              Random rand = new Random();              for (int i = 0; i < codeCount; i++)              {                  if (temp != -1)                  {                      rand = new Random(i * temp * ((int)DateTime.Now.Ticks));                  }                  int t = rand.Next(9);                  if (temp == t)                  {                      return CreateRandomCode(codeCount);                  }                  temp = t;                  randomCode += allCharArray[t];              }              return randomCode;         }

2、数字+字母验证码的实现，代码如下：

view plaincopy to clipboardprint? private string CreateRandomCode(int codeCount)    {        string allChar = "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,W,X,Y,Z,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[] allCharArray = allChar.Split(',');         string randomCode = "";         int temp = -1;         Random rand = new Random();         for (int i = 0; i < codeCount; i++)         {             if (temp != -1)             {                 rand = new Random(i * temp * ((int)DateTime.Now.Ticks));             }             int t = rand.Next(61);             if (temp == t)             {                 return CreateRandomCode(codeCount);             }             temp = t;             randomCode += allCharArray[t];         }         return randomCode;    }           private string CreateRandomCode(int codeCount)         {             string allChar = "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,W,X,Y,Z,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[] allCharArray = allChar.Split(',');              string randomCode = "";              int temp = -1;              Random rand = new Random();              for (int i = 0; i < codeCount; i++)              {                  if (temp != -1)                  {                      rand = new Random(i * temp * ((int)DateTime.Now.Ticks));                  }                  int t = rand.Next(61);                  if (temp == t)                  {                      return CreateRandomCode(codeCount);                  }                  temp = t;                  randomCode += allCharArray[t];              }              return randomCode;         }  

 3、汉字验证码的实现，代码如下：

view plaincopy to clipboardprint? /**/   /* 此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将    四个字节数组存储在object数组中。    参数：strlength，代表需要产生的汉字个数    */       public static object[] CreateRegionCode(int strlength)        {            //定义一个字符串数组储存汉字编码的组成元素             string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };            Random rnd = new Random();            //定义一个object数组用来             object[] bytes = new object[strlength];               /**/           /*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中         每个汉字有四个区位码组成         区位码第1位和区位码第2位作为字节数组第一个元素         区位码第3位和区位码第4位作为字节数组第二个元素        */           for (int i = 0; i < strlength; i++)            {                //区位码第1位                 int r1 = rnd.Next(11, 14);                string str_r1 = rBase[r1].Trim();                   //区位码第2位                 rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值                 int r2;                if (r1 == 13)                {                    r2 = rnd.Next(0, 7);                }                else               {                    r2 = rnd.Next(0, 16);                }                string str_r2 = rBase[r2].Trim();                   //区位码第3位                 rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);                int r3 = rnd.Next(10, 16);                string str_r3 = rBase[r3].Trim();                   //区位码第4位                 rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);                int r4;                if (r3 == 10)                {                    r4 = rnd.Next(1, 16);                }                else if (r3 == 15)                {                    r4 = rnd.Next(0, 15);                }                else               {                    r4 = rnd.Next(0, 16);                }                string str_r4 = rBase[r4].Trim();                   //定义两个字节变量存储产生的随机汉字区位码                 byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);                byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);                //将两个字节变量存储在字节数组中                 byte[] str_r = new byte[] { byte1, byte2 };                   //将产生的一个汉字的字节数组放入object数组中                 bytes.SetValue(str_r, i);            }            return bytes;        }       /**/     /* 此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将      四个字节数组存储在object数组中。      参数：strlength，代表需要产生的汉字个数      */         public static object[] CreateRegionCode(int strlength)         {             //定义一个字符串数组储存汉字编码的组成元素              string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };             Random rnd = new Random();             //定义一个object数组用来              object[] bytes = new object[strlength];

            /**/             /*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中           每个汉字有四个区位码组成           区位码第1位和区位码第2位作为字节数组第一个元素           区位码第3位和区位码第4位作为字节数组第二个元素          */             for (int i = 0; i < strlength; i++)             {                 //区位码第1位                  int r1 = rnd.Next(11, 14);                 string str_r1 = rBase[r1].Trim();

                //区位码第2位                  rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值                  int r2;                 if (r1 == 13)                 {                     r2 = rnd.Next(0, 7);                 }                 else                 {                     r2 = rnd.Next(0, 16);                 }                 string str_r2 = rBase[r2].Trim();

                //区位码第3位                  rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);                 int r3 = rnd.Next(10, 16);                 string str_r3 = rBase[r3].Trim();

                //区位码第4位                  rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);                 int r4;                 if (r3 == 10)                 {                     r4 = rnd.Next(1, 16);                 }                 else if (r3 == 15)                 {                     r4 = rnd.Next(0, 15);                 }                 else                 {                     r4 = rnd.Next(0, 16);                 }                 string str_r4 = rBase[r4].Trim();

                //定义两个字节变量存储产生的随机汉字区位码                  byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);                 byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);                 //将两个字节变量存储在字节数组中                  byte[] str_r = new byte[] { byte1, byte2 };

                //将产生的一个汉字的字节数组放入object数组中                  bytes.SetValue(str_r, i);             }             return bytes;         }

 三、具体实例

前台代码display.aspx

view plaincopy to clipboardprint? <body>        <form id="form1" runat="server">        <div>           <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>            <asp:Image ID="Image1" runat="server" ImageUrl="png.aspx" /><br />            <br />           <asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Button" />            <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">                <asp:ListItem Value="3">默认</asp:ListItem>                <asp:ListItem Value="1">文字</asp:ListItem>                <asp:ListItem Value="2">数字</asp:ListItem>                <asp:ListItem Value="3">混合</asp:ListItem>            </asp:DropDownList></div>        </form>    </body>   <body>     <form id="form1" runat="server">     <div>        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>         <asp:Image ID="Image1" runat="server" ImageUrl="png.aspx" /><br />         <br />        <asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Button" />         <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">             <asp:ListItem Value="3">默认</asp:ListItem>             <asp:ListItem Value="1">文字</asp:ListItem>             <asp:ListItem Value="2">数字</asp:ListItem>             <asp:ListItem Value="3">混合</asp:ListItem>         </asp:DropDownList></div>     </form> </body>

 后台代码display.cs

view plaincopy to clipboardprint? protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)    {        switch (DropDownList1.SelectedValue)        {            case "1":                Image1.ImageUrl = "png.aspx?aa=1";                break;            case "2":                Image1.ImageUrl = "png.aspx?aa=2";                break;            case "3":                Image1.ImageUrl = "png.aspx?aa=3";                break;        }    }    protected void Button2_Click(object sender, EventArgs e)    {        if (TextBox1.Text == Session["gif"].ToString())            Response.Write("OK,正确");        else           Response.Write("验证码不符合");    }           protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)         {             switch (DropDownList1.SelectedValue)             {                 case "1":                     Image1.ImageUrl = "png.aspx?aa=1";                     break;                 case "2":                     Image1.ImageUrl = "png.aspx?aa=2";                     break;                 case "3":                     Image1.ImageUrl = "png.aspx?aa=3";                     break;             }         }         protected void Button2_Click(object sender, EventArgs e)         {             if (TextBox1.Text == Session["gif"].ToString())                 Response.Write("OK,正确");             else                 Response.Write("验证码不符合");         }

后台代码png.cs

view plaincopy to clipboardprint? public partial class png : System.Web.UI.Page    {                 protected void Page_Load(object sender, EventArgs e)        {            switch (Request.QueryString["aa"])            {                case "1":                    gif = stxt(10);                    Session["gif"] = stxt(10);                    break;                case "2":                    gif = GetRandomint(4);                    Session["gif"] = GetRandomint(4);                    break;                case "3":                    gif = CreateRandomCode(4);                    Session["gif"] = CreateRandomCode(4);                    break;                default:                    gif = CreateRandomCode(4);                    Session["gif"] = CreateRandomCode(4);                    break;            }            CreateImage(Session["gif"].ToString());        }           private String GetRandomint(int codeCount)        {            Random random = new Random();            string min = "";            string max = "";            for (int i = 0; i < codeCount; i++)            {                min +="1";                max+="9";            }                return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());        }        /**/       /*    此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将    四个字节数组存储在object数组中。    参数：strlength，代表需要产生的汉字个数    */       public static object[] CreateRegionCode(int strlength)        {            //定义一个字符串数组储存汉字编码的组成元素             string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };            Random rnd = new Random();            //定义一个object数组用来             object[] bytes = new object[strlength];               /**/           /*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中         每个汉字有四个区位码组成         区位码第1位和区位码第2位作为字节数组第一个元素         区位码第3位和区位码第4位作为字节数组第二个元素        */           for (int i = 0; i < strlength; i++)            {                //区位码第1位                 int r1 = rnd.Next(11, 14);                string str_r1 = rBase[r1].Trim();                   //区位码第2位                 rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值                 int r2;                if (r1 == 13)                {                    r2 = rnd.Next(0, 7);                }                else               {                    r2 = rnd.Next(0, 16);                }                string str_r2 = rBase[r2].Trim();                   //区位码第3位                 rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);                int r3 = rnd.Next(10, 16);                string str_r3 = rBase[r3].Trim();                   //区位码第4位                 rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);                int r4;                if (r3 == 10)                {                    r4 = rnd.Next(1, 16);                }                else if (r3 == 15)                {                    r4 = rnd.Next(0, 15);                }                else               {                    r4 = rnd.Next(0, 16);                }                string str_r4 = rBase[r4].Trim();                   //定义两个字节变量存储产生的随机汉字区位码                 byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);                byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);                //将两个字节变量存储在字节数组中                 byte[] str_r = new byte[] { byte1, byte2 };                   //将产生的一个汉字的字节数组放入object数组中                 bytes.SetValue(str_r, i);            }            return bytes;        }        private string stxt(int num)        {            Encoding gb = Encoding.GetEncoding("gb2312");               //调用函数产生10个随机中文汉字编码             object[] bytes = CreateRegionCode(num);            string strtxt = "";               //根据汉字编码的字节数组解码出中文汉字             for (int i = 0; i < num; i++)            {                strtxt += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));            }            return strtxt;        }        /// <summary>        /// 这个是使用字母,数字混合        /// </summary>        /// <param name="VcodeNum"></param>        /// <returns></returns>        private string CreateRandomCode(int codeCount)        {            string allChar = "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,W,X,Y,Z,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[] allCharArray = allChar.Split(',');            string randomCode = "";            int temp = -1;            Random rand = new Random();            for (int i = 0; i < codeCount; i++)            {                if (temp != -1)                {                    rand = new Random(i * temp * ((int)DateTime.Now.Ticks));                }                int t = rand.Next(61);                if (temp == t)                {                    return CreateRandomCode(codeCount);                }                temp = t;                randomCode += allCharArray[t];            }            return randomCode;        }           private void CreateImage(string checkCode)        {            int iwidth = (int)(checkCode.Length * 20);            System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);            Graphics g = Graphics.FromImage(image);            Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);            Brush b = new System.Drawing.SolidBrush(Color.White);            //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);                g.Clear(Color.Black);            g.DrawString(checkCode, f, b, 3, 3);            Pen blackPen = new Pen(Color.Black, 0);            Random rand = new Random();            //for (int i=0;i<5;i++)                //{                    //    int y = rand.Next(image.Height);              //    g.DrawLine(blackPen,0,y,image.Width,y);             //}                    System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);            Response.ClearContent();            Response.ContentType = "image/Jpeg";            Response.BinaryWrite(ms.ToArray());            g.Dispose();            image.Dispose();        }    }       public partial class png : System.Web.UI.Page     {                  protected void Page_Load(object sender, EventArgs e)         {             switch (Request.QueryString["aa"])             {                 case "1":                     gif = stxt(10);                     Session["gif"] = stxt(10);                     break;                 case "2":                     gif = GetRandomint(4);                     Session["gif"] = GetRandomint(4);                     break;                 case "3":                     gif = CreateRandomCode(4);                     Session["gif"] = CreateRandomCode(4);                     break;                 default:                     gif = CreateRandomCode(4);                     Session["gif"] = CreateRandomCode(4);                     break;             }             CreateImage(Session["gif"].ToString());         }

        private String GetRandomint(int codeCount)         {             Random random = new Random();             string min = "";             string max = "";             for (int i = 0; i < codeCount; i++)             {                 min +="1";                 max+="9";             }                 return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());         }         /**/         /*      此函数在汉字编码范围内随机创建含两个元素的十六进制字节数组，每个字节数组代表一个汉字，并将      四个字节数组存储在object数组中。      参数：strlength，代表需要产生的汉字个数      */         public static object[] CreateRegionCode(int strlength)         {             //定义一个字符串数组储存汉字编码的组成元素              string[] rBase = new String[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };             Random rnd = new Random();             //定义一个object数组用来              object[] bytes = new object[strlength];

            /**/             /*每循环一次产生一个含两个元素的十六进制字节数组，并将其放入bject数组中           每个汉字有四个区位码组成           区位码第1位和区位码第2位作为字节数组第一个元素           区位码第3位和区位码第4位作为字节数组第二个元素          */             for (int i = 0; i < strlength; i++)             {                 //区位码第1位                  int r1 = rnd.Next(11, 14);                 string str_r1 = rBase[r1].Trim();

                //区位码第2位                  rnd = new Random(r1 * unchecked((int)DateTime.Now.Ticks) + i);//更换随机数发生器的种子避免产生重复值                  int r2;                 if (r1 == 13)                 {                     r2 = rnd.Next(0, 7);                 }                 else                 {                     r2 = rnd.Next(0, 16);                 }                 string str_r2 = rBase[r2].Trim();

                //区位码第3位                  rnd = new Random(r2 * unchecked((int)DateTime.Now.Ticks) + i);                 int r3 = rnd.Next(10, 16);                 string str_r3 = rBase[r3].Trim();

                //区位码第4位                  rnd = new Random(r3 * unchecked((int)DateTime.Now.Ticks) + i);                 int r4;                 if (r3 == 10)                 {                     r4 = rnd.Next(1, 16);                 }                 else if (r3 == 15)                 {                     r4 = rnd.Next(0, 15);                 }                 else                 {                     r4 = rnd.Next(0, 16);                 }                 string str_r4 = rBase[r4].Trim();

                //定义两个字节变量存储产生的随机汉字区位码                  byte byte1 = Convert.ToByte(str_r1 + str_r2, 16);                 byte byte2 = Convert.ToByte(str_r3 + str_r4, 16);                 //将两个字节变量存储在字节数组中                  byte[] str_r = new byte[] { byte1, byte2 };

                //将产生的一个汉字的字节数组放入object数组中                  bytes.SetValue(str_r, i);             }             return bytes;         }         private string stxt(int num)         {             Encoding gb = Encoding.GetEncoding("gb2312");

            //调用函数产生10个随机中文汉字编码              object[] bytes = CreateRegionCode(num);             string strtxt = "";

            //根据汉字编码的字节数组解码出中文汉字              for (int i = 0; i < num; i++)             {                 strtxt += gb.GetString((byte[])Convert.ChangeType(bytes[i], typeof(byte[])));             }             return strtxt;         }         /// <summary>         /// 这个是使用字母,数字混合         /// </summary>         /// <param name="VcodeNum"></param>         /// <returns></returns>         private string CreateRandomCode(int codeCount)         {             string allChar = "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,W,X,Y,Z,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[] allCharArray = allChar.Split(',');             string randomCode = "";             int temp = -1;             Random rand = new Random();             for (int i = 0; i < codeCount; i++)             {                 if (temp != -1)                 {                     rand = new Random(i * temp * ((int)DateTime.Now.Ticks));                 }                 int t = rand.Next(61);                 if (temp == t)                 {                     return CreateRandomCode(codeCount);                 }                 temp = t;                 randomCode += allCharArray[t];             }             return randomCode;         }

        private void CreateImage(string checkCode)         {             int iwidth = (int)(checkCode.Length * 20);             System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 25);             Graphics g = Graphics.FromImage(image);             Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);             Brush b = new System.Drawing.SolidBrush(Color.White);             //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);                 g.Clear(Color.Black);             g.DrawString(checkCode, f, b, 3, 3);             Pen blackPen = new Pen(Color.Black, 0);             Random rand = new Random();             //for (int i=0;i<5;i++)                 //{                     //    int y = rand.Next(image.Height);               //    g.DrawLine(blackPen,0,y,image.Width,y);              //}                     System.IO.MemoryStream ms = new System.IO.MemoryStream();             image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);             Response.ClearContent();             Response.ContentType = "image/Jpeg";             Response.BinaryWrite(ms.ToArray());             g.Dispose();             image.Dispose();         }     }

四、效果图展示   验证码数字

验证码数字+字母

 验证码汉字