1    private string GenerateCheckCode()
 2    {
 3        int number;
 4        char code;
 5        string checkCode = String.Empty;
 6        Random random = new Random();
 7        for (int i = 0; i < 4; i++)
 8        {
 9            number = random.Next();
10
11            if (number % 2 == 0)
12                code = (char)('0' + (char)(number % 10));
13            else
14                code = (char)('A' + (char)(number % 26));
15
16            checkCode += code.ToString();
17        }
18
19        Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
20        return checkCode;
21    }
22
23

 1   private void CreateCheckCodeImage(string checkCode)
 2    {
 3        if (checkCode == null || checkCode.Trim() == String.Empty)
 4            return;
 5        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);                 Graphics g = Graphics.FromImage(image);
 6        try
 7        {
 8            //生成随机生成器
 9            Random random = new Random();
10            //清空图片背景色
11            g.Clear(Color.White);
12            //画图片的背景噪音线
13            for (int i = 0; i < 2; i++)
14            {
15                int x1 = random.Next(image.Width);
16                int x2 = random.Next(image.Width);
17                int y1 = random.Next(image.Height);
18                int y2 = random.Next(image.Height);
19                g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
20            }
21
22            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
23            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);
24            g.DrawString(checkCode, font, brush, 2, 2);
25            //画图片的前景噪音点
26            for (int i = 0; i < 100; i++)
27            {
28                int x = random.Next(image.Width);
29                int y = random.Next(image.Height);
30                image.SetPixel(x, y, Color.FromArgb(random.Next()));
31            }
32
33            //画图片的边框线
34            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
35            System.IO.MemoryStream ms = new System.IO.MemoryStream();
36            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
37            Response.ClearContent();
38            Response.ContentType = "image/Gif";
39            Response.BinaryWrite(ms.ToArray());
40        }
41        finally
42        {
43            g.Dispose();
44            image.Dispose();
45        }
46    }
47
48

 1    protected void Button1_Click(object sender, EventArgs e)
 2    {
 3        HttpCookie cookie = Request.Cookies["CheckCode"];
 4        if (cookie.Value == this.txtCode.Text.Trim())
 5        {
 6            Response.Write("<script>alert('验证码正确！')</script>");
 7        }
 8        else
 9        {
10            Response.Write("<script>alert('验证码错误！')</script>"); 
11        }
12    }