生成随机数的类2

using System;
using System.Text;
namespace Zhouxiancai
{
 /// <summary>
 /// Class_RandomSecond 的摘要说明。
 /// </summary>
 public class Class_RandomSecond
 {
  public Class_RandomSecond()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   //
  }  
  Random m_rnd = new Random();
  public char getRandomChar()
  {
   int ret = m_rnd.Next(122);
   while (ret < 48 || (ret > 57 && ret < 65) || (ret > 90 && ret < 97))
   {
    ret = m_rnd.Next(122);
   }
   return (char)ret;
  }
  public string getRandomString(int length)
  {
   StringBuilder sb = new StringBuilder(length);
   for (int i = 0; i < length; i++)
   {
    sb.Append(getRandomChar());
   }
   return sb.ToString();
  }  
 }
}