.net中验证码的几种常用方法

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；

一、纯数字验证码的实现

（1）使用随机数方式，代码如下：

View Code

 1 view plaincopy to clipboardprint?
 2 private String GetRandomint(int codeCount)   
 3 {   
 4     Random random = new Random();   
 5     string min = "";   
 6     string max = "";   
 7     for (int i = 0; i < codeCount; i++)   
 8     {   
 9         min +="1";   
10         max+="9";   
11     }   
12         return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());   
13 }  
14         private String GetRandomint(int codeCount)
15         {
16             Random random = new Random();
17             string min = "";
18             string max = "";
19             for (int i = 0; i < codeCount; i++)
20             {
21                 min +="1";
22                 max+="9";
23             }
24                 return (random.Next(Convert.ToInt32(min),Convert.ToInt32(max)).ToString());
25         } 

(2)使用随机组合方式，代码如下

View Code

 1 view plaincopy to clipboardprint?
 2 private string CreateRandomCode(int codeCount)   
 3 {   
 4     string allChar = "0,1,2,3,4,5,6,7,8,9";    
 5     string[] allCharArray = allChar.Split(',');    
 6     string randomCode = "";    
 7     int temp = -1;    
 8     Random rand = new Random();    
 9     for (int i = 0; i < codeCount; i++)    
10     {    
11         if (temp != -1)    
12         {    
13             rand = new Random(i * temp * ((int)DateTime.Now.Ticks));    
14         }    
15         int t = rand.Next(9);    
16         if (temp == t)    
17         {    
18             return CreateRandomCode(codeCount);    
19         }    
20         temp = t;    
21         randomCode += allCharArray[t];    
22     }    
23     return randomCode;   
24 }  
25         private string CreateRandomCode(int codeCount)
26         {
27             string allChar = "0,1,2,3,4,5,6,7,8,9"; 
28             string[] allCharArray = allChar.Split(','); 
29             string randomCode = ""; 
30             int temp = -1; 
31             Random rand = new Random(); 
32             for (int i = 0; i < codeCount; i++) 
33             { 
34                 if (temp != -1) 
35                 { 
36                     rand = new Random(i * temp * ((int)DateTime.Now.Ticks)); 
37                 } 
38                 int t = rand.Next(9); 
39                 if (temp == t) 
40                 { 
41                     return CreateRandomCode(codeCount); 
42                 } 
43                 temp = t; 
44                 randomCode += allCharArray[t]; 
45             } 
46             return randomCode;
47         } 

2、数字+字母验证码的实现

View Code

 1 view plaincopy to clipboardprint?
 2 private string CreateRandomCode(int codeCount)   
 3 {   
 4     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";    
 5     string[] allCharArray = allChar.Split(',');    
 6     string randomCode = "";    
 7     int temp = -1;    
 8     Random rand = new Random();    
 9     for (int i = 0; i < codeCount; i++)    
10     {    
11         if (temp != -1)    
12         {    
13             rand = new Random(i * temp * ((int)DateTime.Now.Ticks));    
14         }    
15         int t = rand.Next(61);    
16         if (temp == t)    
17         {    
18             return CreateRandomCode(codeCount);    
19         }    
20         temp = t;    
21         randomCode += allCharArray[t];    
22     }    
23     return randomCode;   
24 }  
25         private string CreateRandomCode(int codeCount)
26         {
27             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"; 
28             string[] allCharArray = allChar.Split(','); 
29             string randomCode = ""; 
30             int temp = -1; 
31             Random rand = new Random(); 
32             for (int i = 0; i < codeCount; i++) 
33             { 
34                 if (temp != -1) 
35                 { 
36                     rand = new Random(i * temp * ((int)DateTime.Now.Ticks)); 
37                 } 
38                 int t = rand.Next(61); 
39                 if (temp == t) 
40                 { 
41                     return CreateRandomCode(codeCount); 
42                 } 
43                 temp = t; 
44                 randomCode += allCharArray[t]; 
45             } 
46             return randomCode;
47         }
48