在.NET中产生随机密码字符串

using System;
  using System.Security.Cryptography;
  using System.Text;
  
  namespace Utility {
   public class PasswordGenerator {
   public PasswordGenerator() {
   this.Minimum = DefaultMinimum;
   this.Maximum = DefaultMaximum;
   this.ConsecutiveCharacters = false;
   this.RepeatCharacters = true;
   this.ExcludeSymbols = false;
   this.Exclusions = null;
   rng = new RNGCryptoServiceProvider();
   }
  
   protected int GetCryptographicRandomNumber(int lBound, int uBound) {
   // 假定 lBound >= 0 && lBound < uBound
   // 返回一个 int >= lBound and < uBound
   uint urndnum;
   byte[] rndnum = new Byte[4];
  
   if (lBound == uBound-1) {
   // 只有iBound返回的情况
   return lBound;
   }
  
   uint xcludeRndBase = (uint.MaxValue - (uint.MaxValue%(uint)(uBound-lBound)));
   do {
   rng.GetBytes(rndnum);
   urndnum = System.BitConverter.ToUInt32(rndnum,0);
   } while (urndnum >= xcludeRndBase);
   return (int)(urndnum % (uBound-lBound)) + lBound;
   }
  
   protected char GetRandomCharacter() {
   int upperBound = pwdCharArray.GetUpperBound(0);
   if ( true == this.ExcludeSymbols ) {
   upperBound = PasswordGenerator.UBoundDigit;
   }
  
   int randomCharPosition = GetCryptographicRandomNumber(pwdCharArray.GetLowerBound(0), upperBound);
   char randomChar = pwdCharArray[randomCharPosition];
   return randomChar;
   }
  
   public string Generate() {
   // 得到minimum 和 maximum 之间随机的长度
   int pwdLength = GetCryptographicRandomNumber(this.Minimum, this.Maximum);
   StringBuilder pwdBuffer = new StringBuilder();
   pwdBuffer.Capacity = this.Maximum;
   // 产生随机字符
   char lastCharacter, nextCharacter;
   // 初始化标记
   lastCharacter = nextCharacter = 'n';
  
   for ( int i = 0; i < pwdLength; i++ ) {
   nextCharacter = GetRandomCharacter();
   if ( false == this.ConsecutiveCharacters ) {
   while ( lastCharacter == nextCharacter ) {
   nextCharacter = GetRandomCharacter();
   }
   }
  
   if ( false == this.RepeatCharacters ) {
   string temp = pwdBuffer.ToString();
   int duplicateIndex = temp.IndexOf(nextCharacter);
  
   while ( -1 != duplicateIndex ) {
   nextCharacter = GetRandomCharacter();
   duplicateIndex = temp.IndexOf(nextCharacter);
   }
   }
  
   if ( ( null != this.Exclusions ) ) {
   while ( -1 != this.Exclusions.IndexOf(nextCharacter) ) {
   nextCharacter = GetRandomCharacter();
   }
   }
   pwdBuffer.Append(nextCharacter);
   lastCharacter = nextCharacter;
   }
  
  
   if ( null != pwdBuffer ) {
   return pwdBuffer.ToString();
   }
   else {
   return String.Empty;
   }
   }
  
  
   public bool ConsecutiveCharacters {
   get { return this.hasConsecutive; }
   set { this.hasConsecutive = value;}
   }
  
   public bool ExcludeSymbols {
   get { return this.hasSymbols; }
   set { this.hasSymbols = value;}
   }
  
   public string Exclusions {
   get { return this.exclusionSet; }
   set { this.exclusionSet = value; }
   }
  
   public int Maximum {
   get { return this.maxSize; }
   set {
   this.maxSize = value;
   if ( this.minSize >= this.maxSize ) {
   this.maxSize = PasswordGenerator.DefaultMaximum;
   }
   }
   }
  
   public int Minimum {
   get { return this.minSize; }
   set {
   this.minSize = value;
   if ( PasswordGenerator.DefaultMinimum > this.minSize ) {
   this.minSize = PasswordGenerator.DefaultMinimum;
   }
   }
   }
  
   public bool RepeatCharacters {
   get { return this.hasRepeating; }
   set { this.hasRepeating = value;}
   }
  
  
   private const int DefaultMaximum = 10;
   private const int DefaultMinimum = 6;
   private const int UBoundDigit = 61;
   private string exclusionSet;
   private bool hasConsecutive;
   private bool hasRepeating;
   private bool hasSymbols;
   private int maxSize;
   private int minSize;
   private char[] pwdCharArray = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567
  89`~!@#$^*()-_=+[]{}\|;:'",./".ToCharArray();
   private RNGCryptoServiceProvider rng;
   }
  }