.net实现验证码功能

　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：　

        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：

        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：

        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： 

        /**/
        /* 
    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　

<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>

 

        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");
        }

    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();
        }
    }

　

<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>

        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");
        }

    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