学步园

汉字验证码比字母或数字的验证码更先进，更有效的防止非法注册。。。

示例如下：
同样添加一个Image控件，ＨＴＭＬ属性如下：
<asp:Image ID="Image1" src="CheckCode.aspx" runat="server" Height="21px" Width="85px" />

CheckCode.aspx文件源代码如下：

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.Text;  //添加引用
using System.Drawing;  //添加引用

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        GraphicsImage(4);  //调用方法生成四位汉字验证码
    }

    private object[] CreateString(int strlength)
    {
        //定义一个数组存储汉字编码的组成元素
        string[] str = new string[16] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };

        Random ran = new Random();  //定义一个随机数对象
        object[] bytes = new object[strlength];
        for (int i = 0; i < strlength; i++)
        {
            //获取区位码第一位
            int ran1 = ran.Next(11, 14);
            string str1 = str[ran1].Trim();

            //获取区位码第二位并防止数据重复
            ran = new Random(ran1 * unchecked((int)DateTime.Now.Ticks) + i);
            int ran2;
            if (ran1 == 13)
            {
                ran2 = ran.Next(0, 7);
            }
            else
            {
                ran2 = ran.Next(0, 16);
            }
            string str2 = str[ran2].Trim();

            //获取区位码第三位
            ran = new Random(ran2 * unchecked((int)DateTime.Now.Ticks) + i);
            int ran3 = ran.Next(10, 16);
            string str3 = str[ran3].Trim();

            //获取区位码第四位
            ran = new Random(ran3 * unchecked((int)DateTime.Now.Ticks) + i);
            int ran4;
            if (ran3 == 10)
            {
                ran4 = ran.Next(1, 16);
            }
            else if (ran3 == 15)
            {
                ran4 = ran.Next(0, 15);
            }
            else
            {
                ran4 = ran.Next(0, 16);
            }
            string str4 = str[ran4].Trim();

            //定义字节变量存储产生的随机汉字区位码
            byte byte1 = Convert.ToByte(str1 + str2, 16);
            byte byte2 = Convert.ToByte(str3 + str4, 16);

            byte[] stradd = new byte[] { byte1,byte2};
            //将产生的汉字字节放入数组
            bytes.SetValue(stradd, i);
        }
        return bytes;
    }

    private string GetString(int length)
    {
        Encoding gb = Encoding.GetEncoding("gb2312");
        object[] bytes = CreateString(length);

        //根据汉字字节解码出中文汉字
        string str1 = gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[])));
        string str2 = gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[])));
        string str3 = gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[])));
        string str4 = gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[])));

        string str = str1 + str2 + str3 + str4;
        Response.Cookies.Add(new HttpCookie("CheckCode", str));
        return str;
    }

    private void GraphicsImage(int length)
    {
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((GetString(length).Length * 22.5)), 22);
        Graphics g = Graphics.FromImage(image);  //创建画布

        try
        {
            //生成随机生成器
            Random random = new Random();

            //清空图片背景色
            g.Clear(Color.White);

            //画图片的背景噪音线
            for (int i = 0; i < 1; i++)
            {
                int x1 = random.Next(image.Width);
                int x2 = random.Next(image.Width);
                int y1 = random.Next(image.Height);
                int y2 = random.Next(image.Height);

                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
            }

            Font font = new System.Drawing.Font("Couriew New", 12, System.Drawing.FontStyle.Bold );
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush
                (new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            g.DrawString(GetString(length), font, brush, 2, 2);

            //画图片的前景噪音点
            for (int i = 0; i < 50; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);

                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        catch (Exception ms)
        {
            Response.Write(ms.Message);
        }

    }
}
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http://www.yxsoft.net.cn/article.asp?id=12