生成随机码类 （全）

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System.Text;

namespace Byecity2011.WebSite.Utils
{
    /// <summary>
    /// 生成随机码类
    /// </summary>
    public class RandomObj
    {
        /// <summary>
        ///
        /// </summary>
        public RandomObj()
        {
        }

        #region 数字随机数
        /// <summary>
        /// 数字随机数
        /// </summary>
        /// <param name="n">生成长度</param>
        /// <returns></returns>
        public static string RandNum(int n)
        {
            char[] arrChar = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
            StringBuilder num = new StringBuilder();

            Random rnd = new Random(DateTime.Now.Millisecond);

            for (int i = 0; i < n; i++)
            {
                num.Append(arrChar[rnd.Next(0, 9)].ToString());

            }

            return num.ToString();
        }
        #endregion

        #region 数字和字母随机数
        /// <summary>
        /// 数字和字母随机数
        /// </summary>
        /// <param name="n">生成长度</param>
        /// <returns></returns>
        public static string RandCode(int n)
        {
            char[] arrChar = new char[]{
           'a','b','d','c','e','f','g','h','i','j','k','l','m','n','p','r','q','s','t','u','v','w','z','y','x',
           '0','1','2','3','4','5','6','7','8','9',
           'A','B','C','D','E','F','