生成N位数字随机数

//生成N位的随机数 全数字
    private string GetRandom(int len)
    {
        string k = "";
        Random rand = new Random(GetRandomSeed());
        for (int i = 0; i < len; i++)
        {
            k += rand.Next(0, 10).ToString();
        }
        return k;
    }
    //取随机数种子
    private int GetRandomSeed()
    {
        byte[] bytes = new byte[4];
        System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
        rng.GetBytes(bytes);
        return BitConverter.ToInt32(bytes, 0);
    }