关于C# 的高效随机字符串

ArLi2003 csdn 2003-6-14

使用RNGCryptoServiceProvider 做种，可以在一秒内产生的随机数重复率非常的低，对于以往使用时间做种的方法是个升级，代码如下：

using System;
using System.Security.Cryptography;

namespace ArLi.CommonPrj
{
    /// <summary>
    /// 随机密码
    /// </summary>
    public sealed class RandomStr
    {
        public const string myVersion = "1.2";

        /********
        * Const and Function
        * ********/
        private static readonly int defaultLength = 8;

        private static int GetNewSeed()
        {
            byte[] rndBytes = new byte[4];
            RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
            rng.GetBytes(rndBytes);
            return BitConverter.ToInt32(rndBytes, 0);
        }

        /********
        * getRndCode of all char .
        * ********/
        private static string BuildRndCodeAll(int strLen)
        {
            System.Random RandomObj = new System.Random(GetNewSeed());
            string buildRndCodeReturn = null;
            for (int i = 0; i < strLen; i++)
            {
                buildRndCodeReturn += (char)RandomObj.Next(33, 125);
            }
            return buildRndCodeReturn;
        }

        public static string GetRndStrOfAll()
        {
            return BuildRndCodeAll(defaultLength);
        }

        public static string GetRndStrOfAll(int LenOf)
        {
            return BuildRndCodeAll(LenOf);
        }

        /********
        * getRndCode of only .
        * ********/
        private static string sCharLow = "abcdefghijklmnopqrstuvwxyz";
        private static string sCharUpp = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        private static string sNumber = "0123456789";

        private static string BuildRndCodeOnly(string StrOf, int strLen)
        {
            System.Random RandomObj = new System.Random(GetNewSeed());
            string buildRndCodeReturn = null;
            for (int i = 0; i < strLen; i++)
            {
                buildRndCodeReturn += StrOf.Substring(RandomObj.Next(0, StrOf.Length - 1), 1);
            }
            return buildRndCodeReturn;
        }

        public static string GetRndStrOnlyFor()
        {
            return BuildRndCodeOnly(sCharLow + sNumber, defaultLength);
        }

        public static string GetRndStrOnlyFor(int LenOf)
        {
            return BuildRndCodeOnly(sCharLow + sNumber, LenOf);
        }

        public static string GetRndStrOnlyFor(bool bUseUpper, bool bUseNumber)
        {
            string strTmp = sCharLow;
            if (bUseUpper) strTmp += sCharUpp;
            if (bUseNumber) strTmp += sNumber;

            return BuildRndCodeOnly(strTmp, defaultLength);
        }

        public static string GetRndStrOnlyFor(int LenOf, bool bUseUpper, bool bUseNumber)
        {
            string strTmp = sCharLow;
            if (bUseUpper) strTmp += sCharUpp;
            if (bUseNumber) strTmp += sNumber;

            return BuildRndCodeOnly(strTmp, LenOf);
        }
    }
}