（1） using System;namespace ConsoleApplication1{ class Class1 {  static void Main(string[] args)  {         Random random = new Random();      int a = random.Next(1, 10);      Console.WriteLine(a.ToString());      Console.ReadLine();  } }}  （2） //stringbuilder 是我加的，不要每次都生成一个新对象浪费空间。 public string GenerateCheckCode()       {             int number;           char code;           string checkCode = String.Empty;           StringBuilder checkcode = new StringBuilder();            System.Random random = new Random();            for (int i = 0; i < 5; i++)            {               number = random.Next(); //如果是奇数 就生成字母，否则生成数字。                if (number % 2 == 0)                   code = (char)('0' + (char)(number % 10));               else                   code = (char)('A' + (char)(number % 26));                checkCode += code.ToString();               checkcode.Append(code.ToString());           }            /**////用于客户端校验码比较           Session["CheckCode"] = checkcode;                      string check = checkcode.ToString();           code1 = check;           return check;      }            3. 产生62位内任意数字大小写字母的随机数       private   static   char[]   constant=         {           '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','v','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'         };         public   static   string   GenerateRandom(int   Length)         {                 System.Text.StringBuilder   newRandom   =   new   System.Text.StringBuilder(62);           Random   rd=   new   Random();           for(int   i=0;i<Length;i++)           {             newRandom.Append(constant[rd.Next(62)]);           }           return   newRandom.ToString();         }   要是只要字母，改为如下：       private   static   char[]   constant=         {           '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',           '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'         };         public   static   string   GenerateRandom(int   Length)         {                 System.Text.StringBuilder   newRandom   =   new   System.Text.StringBuilder(52);           Random   rd=   new   Random();           for(int   i=0;i<Length;i++)           {             newRandom.Append(constant[rd.Next(52)]);           }           return   newRandom.ToString();         }         //调用---------------     sting   str=GenerateRandom(6); 4. 改造一下,可自由选择生成随机字母类型 private static char[] constant = { '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','v','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' }; public enum RandomType { All, Number, Uppercased, Lowercased, NumberAndUppercased, NumberAndLowercased, UppercasedAndLowercased, } public static string GenerateRandom(int Length,RandomType rt) { int initsize=0; int beginsize = 0; int endsize=0; Boolean IsCross=false; switch (rt) { case RandomType.All: { initsize = 62; beginsize = 1; endsize = 62; //IsCross = false; break; } case RandomType.Lowercased: { initsize = 26; beginsize = 11; endsize = 36; //IsCross = false; break; } case RandomType.Uppercased: { initsize = 26; beginsize = 37; endsize = 62; // IsCross = false; break; } case RandomType.Number: { initsize = 10; beginsize = 1; endsize = 10; //IsCross = false; break; } case RandomType.UppercasedAndLowercased: { initsize = 52; beginsize = 11; endsize = 62; //IsCross = false; break; } case RandomType.NumberAndLowercased: { initsize = 36; beginsize = 1; endsize = 36; //IsCross = false; break; } case RandomType.NumberAndUppercased: { IsCross = true; break; } } System.Text.StringBuilder newRandom = new System.Text.StringBuilder(initsize); Random rd = new Random(); if (!IsCross) { for (int i = 0; i < Length; i++) { newRandom.Append(constant[rd.Next(beginsize, endsize)]); } } else { for (int i = 0; i < Length; i++) { newRandom.Append(constant[rd.Next(1, 10)]); newRandom.Append(constant[rd.Next(37, 62)]); } } return newRandom.ToString(); }

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