ASP.net生成各种随机数字，用于优惠券、验证码等

 private long GenerateId()
    {
        byte[] buffer = Guid.NewGuid().ToByteArray();
        return BitConverter.ToInt32(buffer, 0);
    }

 private string GenerateId(string flag)
    {
        long i = 1;
        foreach (byte b in Guid.NewGuid().ToByteArray())
        {
            i *= ((int)b + 1);
        }
        return string.Format("{0:x}", i - DateTime.Now.Ticks);
    } 

public class RandomNum
{
    private static char[] constant ={
            '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','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'
        };
    public static string GenerateRandom(int Length)
    {
        System.Text.StringBuilder newRandom = new System.Text.StringBuilder(62);
        Random rd = new Random();
        for (int i = 0; i < Length; i++)
        {
            newRandom.Append(constant[rd.Next(62)]);
        }
        return newRandom.ToString();
    }
}

/// <summary>
/// 生成不重复乱码 
/// </summary>
public class RandomNumber
{
    const long MAX = 218340105584895; // ZZZZZZZZ
    const long MIN = 568002355840; // 0a0000000
    const int SeedQuantity = 1; // 随机质量，越大越慢，即使为1质量也不错


    public static long[] getRandom(int size)
    {
        //先取一定倍量的随机种子，再从这些种子里面随机
        long[] seed = getRandomSeeds(size * SeedQuantity);
        long[] ranArr = new long[size];


        Random rand = new Random();
        for (int i = 0; i < size; i++)
        {
            int j = rand.Next(seed.Length - i);
            ranArr[i] = seed[j];
            seed[j] = seed[seed.Length - 1 - i];
        }
        return ranArr;
    }


    private static long[] getRandomSeeds(int size)
    {
        long[] ranArr = new long[size];
        for (int i = 0; i < size; i++)
        {
            ranArr[i] = GetNext(i);
        }
        Array.Sort(ranArr); // 排序


        List<int> seedRepeatPosition = new List<int>();
        // 遍历一遍将重复的记录下来
        long last = 0;
        for (int i = 0; i < ranArr.Length; i++)
        {
            if (ranArr[i] == last)
            {
                ranArr[i] = 0;
                seedRepeatPosition.Add(i);
            }
            else
                last = ranArr[i];
        }


        Array.Sort(ranArr); // 排序
        // 将重复的重新处理为不重复的
        List<long> newseedList = new List<long>();
        long newseed;
        for (int i = 0; i < seedRepeatPosition.Count; i++)
        {
            do
            {


                newseed = GetNext(i);
            } while (Array.BinarySearch(ranArr, newseed) > -1 || newseedList.Contains(newseed));


            newseedList.Add(newseed);
            ranArr[seedRepeatPosition[i]] = newseed;


        }


        return ranArr;


    }
    private static long GetNext(int seed)
    {
        int initSeed = (int)(DateTime.Now.Ticks - seed * 10000);
        Random ran = new Random(initSeed);
        double d;
        long ret;


        do
        {
            d = ran.NextDouble();
            ret = Convert.ToInt64(d * (Math.Pow(10, 15)));
        }
        while (ret <= MIN || ret > MAX);


        return ret;
    }
}

/// <summary>
/// 取时间戳生成随即数生成10位流水号
/// </summary>
/// <returns></returns>
public static UInt32 UnixStamp()
{
    TimeSpan ts = DateTime.Now - TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970, 1, 1));
    return Convert.ToUInt32(ts.TotalSeconds);
}

/// <summary>
/// 取随机数
/// </summary>
/// <param name="length"></param>
/// <returns></returns>
public static string BuildRandomStr(int length)
{
    Random rand = new Random();

    int num = rand.Next();

    string str = num.ToString();

    if (str.Length > length)
    {
        str = str.Substring(0, length);
    }
    else if (str.Length < length)
    {
        int n = length - str.Length;
        while (n > 0)
        {
            str.Insert(0, "0");
            n--;
        }
    }

    return str;
}

/// 获取时间戳  
/// </summary>  
/// <returns></returns>  
public static string GetTimeStamp()  
{  
    TimeSpan ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);  
    return Convert.ToInt64(ts.TotalSeconds).ToString();  
}