C#后台生成验证码

https://www.cnblogs.com/vchenpeng/archive/2013/05/12/3074887.html

  /// <summary>  
        /// 获取时间戳  
        /// </summary>  
        /// <returns></returns>  
        public static string GetTimeStamp()
        {
            TimeSpan ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            return Convert.ToInt64(ts.TotalSeconds).ToString();
        }
        /// <summary>
        /// 获取验证码
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string getCode(this string str)
        {
            int number;
            char code;
            string checkCode = String.Empty;  
            Random random = new Random();
            foreach (char c in str)
            {
                number = random.Next();
                if (c % 2 == 0)
                {
                    code = (char)('0' + (char)(number % 10));
                    if (System.Text.RegularExpressions.Regex.IsMatch(code.ToString(), "^[0-9]+$"))
                    {
                        checkCode += code;
                    }
                }
                else
                {
                     code = (char)('C' + (char)(number % 26));
                    if (System.Text.RegularExpressions.Regex.IsMatch(code.ToString(), "^[A-Z]+$"))
                    {
                        checkCode += code;
                    }
                }
            }
            return checkCode;
        }

　/// <summary>
 2         /// 动态生成指定数目的随机数或字母
 3         /// </summary>
 4         /// <param name="num">整数</param>
 5         /// <returns>返回验证码字符串</returns>
 6         private string GenerateCheckCode(int num)
 7         {
 8             int number;  //定义变量
 9             char code;
10             string checkCode = String.Empty;  //空字符串，只读
11             Random random = new Random();    //定义随机变量实例
12             for (int i=0; i < num;i++ )
13             {
14                 //利用for循环生成指定数目的随机数或字母
15                 number = random.Next(); //返回一个小于指定的最大值的非负的随机数 next有三个构造函数 
16                 if (number % 2 == 0)
17                 {
18                     //产生一个一位数
19                     code = (char)('0' + (char)(number % 10));
20                 }
21                 else
22                 { 
23                     //产生一个字母
24                     code = (char)('C'+(char)(number % 26));
25                 }
26                 checkCode += code.ToString();
27             }
28             return checkCode;
29         }