比较方便的生成指定长度数字和字母混合的随机数

namespace NetCMS.Common  
{  
  public class Rand  
  {  
  /// <summary>  
  /// 生成随机数字  
  /// </summary>  
  /// <param name="length">生成长度</param>  
  /// <returns></returns>  
  public static string Number(int Length)  
  {  
  return Number(Length, false);  
  }  
   
  /// <summary>  
  /// 生成随机数字  
  /// </summary>  
  /// <param name="Length">生成长度</param>  
  /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>  
  /// <returns></returns>  
  public static string Number(int Length,bool Sleep)  
  {  
  if(Sleep)  
  System.Threading.Thread.Sleep(3);  
  string result = "";  
  System.Random random = new Random();  
  for (int i = 0; i < Length; i++)  
  {  
  result += random.Next(10).ToString();  
  }  
  return result;  
  }  
   
  /// <summary>  
  /// 生成随机字母与数字  
  /// </summary>  
  /// <param name="IntStr">生成长度</param>  
  /// <returns></returns>  
  public static string Str(int Length)  
  {  
  return Str(Length, false);  
  }  
  /// <summary>  
  /// 生成随机字母与数字  
  /// </summary>  
  /// <param name="Length">生成长度</param>  
  /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>  
  /// <returns></returns>  
  public static string Str(int Length, bool Sleep)  
  {  
  if(Sleep)  
  System.Threading.Thread.Sleep(3);  
  char[] Pattern = new char[] { '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' };  
  string result = "";  
  int n = Pattern.Length;  
  System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));  
  for (int i = 0; i < Length; i++)  
  {  
  int rnd = random.Next(0,n);  
  result += Pattern[rnd];  
  }  
  return result;  
  }  
   
   
  /// <summary>  
  /// 生成随机纯字母随机数  
  /// </summary>  
  /// <param name="IntStr">生成长度</param>  
  /// <returns></returns>  
  public static string Str_char(int Length)  
  {  
  return Str_char(Length, false);  
  }  
   
  /// <summary>  
  /// 生成随机纯字母随机数  
  /// </summary>  
  /// <param name="Length">生成长度</param>  
  /// <param name="Sleep">是否要在生成前将当前线程阻止以避免重复</param>  
  /// <returns></returns>  
  public static string Str_char(int Length, bool Sleep)  
  {  
  if (Sleep)  
  System.Threading.Thread.Sleep(3);  
  char[] Pattern = new char[] { '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' };  
  string result = "";  
  int n = Pattern.Length;  
  System.Random random = new Random(~unchecked((int)DateTime.Now.Ticks));  
  for (int i = 0; i < Length; i++)  
  {  
  int rnd = random.Next(0, n);  
  result += Pattern[rnd];  
  }  
  return result;  
  }  
  }