(转)验证码

 1CheckCode.aspx.cs
 2/**//*********************************************************************/
 3using System;
 4using System.Data;
 5using System.Configuration;
 6using System.Collections;
 7using System.Web;
 8using System.Web.Security;
 9using System.Web.UI;
10using System.Web.UI.WebControls;
11using System.Web.UI.WebControls.WebParts;
12using System.Web.UI.HtmlControls;
13using System.Drawing;
14public partial class CheckCode : System.Web.UI.Page
15{
16    private void Page_Load(object sender, System.EventArgs e)
17    {
18        this.CreateCheckCodeImage(GenerateCheckCode());
19    }
20    private string GenerateCheckCode()
21    {
22        int number;
23        char code;
24        string checkCode = String.Empty;
25        System.Random random = new Random();
26        for (int i = 0; i < 5; i++)
27        {
28            number = random.Next();
29            if (number % 2 == 0)
30                code = (char)('0' + (char)(number % 10));
31            else
32                code = (char)('A' + (char)(number % 26));
33            checkCode += code.ToString();
34        }
35        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
36        return checkCode;
37    }
38    private void CreateCheckCodeImage(string checkCode)
39    {
40        if (checkCode == null || checkCode.Trim() == String.Empty)
41            return;
42        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
43        Graphics g = Graphics.FromImage(image);
44        try
45        {
46            //生成随机生成器
47            Random random = new Random();
48            //清空图片背景色
49            g.Clear(Color.White);
50            //画图片的背景噪音线
51            for (int i = 0; i < 25; i++)
52            {
53                int x1 = random.Next(image.Width);
54                int x2 = random.Next(image.Width);
55                int y1 = random.Next(image.Height);
56                int y2 = random.Next(image.Height);
57
58                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
59            }
60            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
61            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);
62            g.DrawString(checkCode, font, brush, 2, 2);
63            //画图片的前景噪音点
64            for (int i = 0; i < 100; i++)
65            {
66                int x = random.Next(image.Width);
67                int y = random.Next(image.Height);
68
69                image.SetPixel(x, y, Color.FromArgb(random.Next()));
70            }
71            //画图片的边框线
72            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
73            System.IO.MemoryStream ms = new System.IO.MemoryStream();
74            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
75            Response.ClearContent();
76            Response.ContentType = "image/Gif";
77            Response.BinaryWrite(ms.ToArray());
78        }
79        finally
80        {
81            g.Dispose();
82            image.Dispose();
83        }
84    }
85}
登录页面中使用“<ImageButton>” 这个 HTML 元素来显示生成的验证码图片：<asp:ImageButton ID="ImageButton1" ImageUrl="CheckCode.aspx" runat="server"/>
在登录页面的登录按钮的处理事件中使用以下代码判断验证码：
private void btnLogin_Click(object sender, System.Web.UI.ImageClickEventArgs e)
  {
   if(Request.Cookies["CheckCode"] == null)
   {
    lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";
    lblMessage.Visible = true;
    return;
   }

   if(String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)
   {
    lblMessage.Text = "验证码错误，请输入正确的验证码。";
    lblMessage.Visible = true;
    return;
   }
 }
http://www.spdevelop.com/forum/Answer.aspx?QuestionId=38