ASP.NET生成验证码
生成验证码原理：产生随机字符，并将字符生成为图片，同时储存到Session里去，然后验证用户输入的内容是否与Session中的验证码相符即可。
效果图：用户可以点击切换验证码信息。
一般处理程序：CheckCodeHandler.cs
1 <%@ WebHandler Language="C#" Class="CheckCodeHandler" %>
2
3 using System;
4 using System.Web;
5 using System.Text;
6 using System.Drawing;
7 using System.Web.SessionState;
8
9 public class CheckCodeHandler : IHttpHandler,IRequiresSessionState
10 {
11
12 //产生验证码的字符集
13 public string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
14
15 public void ProcessRequest (HttpContext context) {
16 string validateCode = CreateRandomCode(4);
17 context.Session["ValidateCode"] = validateCode;//将验证码保存到session中
18 CreateCodeImage(validateCode, context);
19 }
20
21 public bool IsReusable {
22 get {
23 return false;
24 }
25 }
26
27 /// <summary>
28 /// 生成验证码
29 /// </summary>
30 /// <param name="n">验证码个数</param>
31 /// <returns>验证码字符串</returns>
32 public string CreateRandomCode(int n)
33 {
34 string[] CharArray = charcode.Split(',');//将字符串转换为字符数组
35 string randomCode = "";
36 int temp = -1;
37
38 Random rand = new Random();
39 for (int i = 0; i < n; i++)
40 {
41 if (temp != -1)
42 {
43 rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
44 }
45 int t = rand.Next(CharArray.Length - 1);
46 if (temp != -1 && temp == t)
47 {
48 return CreateRandomCode(n);
49 }
50 temp = t;
51 randomCode += CharArray[t];
52 }
53 return randomCode;
54 }
55
56 public void CreateCodeImage(string checkCode, HttpContext context)
57 {
58 int iwidth = (int)(checkCode.Length * 13);
59 System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
60 Graphics g = Graphics.FromImage(image);
61 Font f = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Italic | System.Drawing.FontStyle.Bold));
62
63 // 前景色
64 Brush b = new System.Drawing.SolidBrush(Color.Black);
65
66 // 背景色
67 g.Clear(Color.White);
68
69 // 填充文字
70 g.DrawString(checkCode, f, b, 0, 1);
71
72 // 随机线条
73
74 Pen linePen = new Pen(Color.Gray, 0);
75 Random rand = new Random();
76
77 for (int i = 0; i < 5; i++)
78 {
79 int x1 = rand.Next(image.Width);
80 int y1 = rand.Next(image.Height);
81 int x2 = rand.Next(image.Width);
82 int y2 = rand.Next(image.Height);
83 g.DrawLine(linePen, x1, y1, x2, y2);
84 }
85
86 // 随机点
87 for (int i = 0; i < 30; i++)
88 {
89 int x = rand.Next(image.Width);
90 int y = rand.Next(image.Height);
91 image.SetPixel(x, y, Color.Gray);
92 }
93
94 // 边框
95 g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);
96
97 // 输出图片
98 System.IO.MemoryStream ms = new System.IO.MemoryStream();
99 image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
100 context.Response.ClearContent();
101 context.Response.ContentType = "image/jpeg";
102 context.Response.BinaryWrite(ms.ToArray());
103 g.Dispose();
104 image.Dispose();
105 }
106 }
封装成类库：ValidateNumber.cs
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Web;
5 using System.Drawing;
6 using System.Web.UI;
7 using System.Drawing.Drawing2D;
8 using System.IO;
9 using System.Drawing.Imaging;
10
11 /// <summary>
12 ///ValidateNumber 生成验证码
13 /// </summary>
14 public class ValidateNumber
15 {
16 //产生验证码的字符集 （易混淆的字符去掉）
17 private string charcode = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y,a,b,c,d,e,f,g,h,j,k,m,n,p,r,s,u,w,x,y";
18
19 /// <summary>
20 /// 验证码的最大长度
21 /// </summary>
22 public int MaxLength
23 {
24 get { return 10; }
25 }
26
27 /// <summary>
28 /// 验证码的最小长度
29 /// </summary>
30 public int MinLength
31 {
32 get { return 1; }
33 }
34
35 /// <summary>
36 /// 生成验证码
37 /// </summary>
38 /// <param name="length">指定验证码的长度</param>
39 /// <returns></returns>
40 public string CreateValidateNumber(int length)
41 {
42 string[] CharArray = charcode.Split(',');//将字符串转换为字符数组
43 string randomCode = "";
44 int temp = -1;
45
46 Random rand = new Random();
47 for (int i = 0; i < length; i++)
48 {
49 if (temp != -1)
50 {
51 rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
52 }
53 int t = rand.Next(CharArray.Length - 1);
54 if (temp != -1 && temp == t)
55 {
56 return CreateValidateNumber(length);
57 }
58 temp = t;
59 randomCode += CharArray[t];
60 }
61 return randomCode;
62 }
63
64 /// <summary>
65 /// 创建验证码的图片
66 /// </summary>
67 /// <param name="context">context对象</param>
68 /// <param name="validateNum">验证码</param>
69 public void CreateValidateGraphic(HttpContext context,string validateNum)
70 {
71 int iwidth = (int)(validateNum.Length * 14);
72 Bitmap image = new Bitmap(iwidth, 22);
73 Graphics g = Graphics.FromImage(image);
74 try
75 {
76 //生成随机生成器
77 Random random = new Random();
78 //清空图片背景色
79 g.Clear(Color.White);
80 //画图片的干扰线
81 for (int i = 0; i < 25; i++)
82 {
83 int x1 = random.Next(image.Width);
84 int x2 = random.Next(image.Width);
85 int y1 = random.Next(image.Height);
86 int y2 = random.Next(image.Height);
87 g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
88 }
89 Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
90 LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),
91 Color.Blue, Color.DarkRed, 1.2f, true);
92 g.DrawString(validateNum, font, brush, 3, 2);
93 //画图片的前景干扰点
94 for (int i = 0; i < 100; i++)
95 {
96 int x = random.Next(image.Width);
97 int y = random.Next(image.Height);
98 image.SetPixel(x, y, Color.FromArgb(random.Next()));
99 }
100 //画图片的边框线
101 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
102 //保存图片数据
103 MemoryStream stream = new MemoryStream();
104 image.Save(stream, ImageFormat.Jpeg);
105 //输出图片
106 context.Response.Clear();
107 context.Response.ContentType = "image/jpeg";
108 context.Response.BinaryWrite(stream.ToArray());
109 }
110 finally
111 {
112 g.Dispose();
113 image.Dispose();
114 }
115 }
116 /// <summary>
117 /// 得到验证码图片的长度
118 /// </summary>
119 /// <param name="validateNumLength">验证码的长度</param>
120 /// <returns></returns>
121 public static int GetImageWidth(int validateNumLength)
122 {
123 return (int)(validateNumLength * 14);
124 }
125 /// <summary>
126 /// 得到验证码图片的高度
127 /// </summary>
128 /// <returns></returns>
129 public static double GetImageHeight()
130 {
131 return 22;
132 }
133 }
示例下载：http://up.2cto.com/2012/0528/20120528090736627.rar
作者： ForEvErNoME