自定義C#類產生不重復的隨機字符串

這個C#類用于隨機產生不重復的字符串，可以指定字符串范圍，可以指定要產生字符串的長度

using System;

namespace DotNet.Utilities
{
    public class RandomOperate
    {
        // 一：隨機生成不重復數字字符串 
        private int rep = 0;
        public string GenerateCheckCodeNum(int codeCount)
        {
            string str = string.Empty;
            long num2 = DateTime.Now.Ticks + this.rep;
            this.rep++;
            Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep)));
            for (int i = 0; i < codeCount; i++)
            {
                int num = random.Next();
                str = str + ((char)(0x30 + ((ushort)(num % 10)))).ToString();
            }
            return str;
        }

    //方法二：隨機生成字符串（數字和字母混和）
    public string GenerateCheckCode(int codeCount)
    {
        string str = string.Empty;
        long num2 = DateTime.Now.Ticks + this.rep;
        this.rep++;
        Random random = new Random(((int)(((ulong)num2) & 0xffffffffL)) | ((int)(num2 >> this.rep)));
        for (int i = 0; i < codeCount; i++)
        {
            char ch;
            int num = random.Next();
            if ((num % 2) == 0)
            {
                ch = (char)(0x30 + ((ushort)(num % 10)));
            }
            else
            {
                ch = (char)(0x41 + ((ushort)(num % 0x1a)));
            }
            str = str + ch.ToString();
        }
        return str;
    }

    #region

    /// <summary>
    /// 從字符串里隨機得到，規定個數的字符串.
    /// </summary>
    /// <param name="allChar"></param>
    /// <param name="CodeCount"></param>
    /// <returns></returns>
    private string GetRandomCode(string allChar, int CodeCount)
    {
        //string allChar = "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[] allCharArray = allChar.Split(',');
        string RandomCode = "";
        int temp = -1;
        Random rand = new Random();
        for (int i = 0; i < CodeCount; i++)
        {
            if (temp != -1)
            {
                rand = new Random(temp * i * ((int)DateTime.Now.Ticks));
            }

            int t = rand.Next(allCharArray.Length - 1);

            while (temp == t)
            {
                t = rand.Next(allCharArray.Length - 1);
            }

            temp = t;
            RandomCode += allCharArray[t];
        }
        return RandomCode;
    }

    #endregion
}

}</pre>