asp.net实现网站验证码功能

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());
}

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;
}

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;
}

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;
    }

/**/ /* 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

<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

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

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