C# 生产随机数 --几乎可以做到不重复

十年河东，十年河西，莫欺少年穷

学无止境，精益求精

代码如下：

  class Program
    {
        static int seed = 13;
        static ThreadLocal<Random> threadLocal = new ThreadLocal<Random>(() => new Random(Interlocked.Increment(ref seed)));
        public static int GetTid(int length = 6)
        {
            var maxLen = int.MaxValue.ToString().Length;
            if (length > maxLen)
            {
                return 0;
            }
            var TxID = Math.Abs(threadLocal.Value.Next() - Convert.ToInt32(DateTime.Now.ToString("HHmmssfff")));
            var len = TxID.ToString().Length;
            if (len >= length)
            {
                return Convert.ToInt32(TxID.ToString().Substring(0, length));
            }
            return new Random(seed).Next(Convert.ToInt32(Math.Pow(10, length - 1)), Convert.ToInt32(Math.Pow(10, length)) - 1);
        }
        public static void Main(string[] args)
        {
            
            for(var i = 0; i < 100; i++)
            {
                Console.WriteLine("四位数字为：" + GetTid(4));
            }
            Console.ReadLine();
        }

    }

核心代码：

  var TxID = Math.Abs(threadLocal.Value.Next() - Convert.ToInt32(DateTime.Now.ToString("HHmmssfff")));

不信你看嘛

public static void Main(string[] args)
        {
            List<int> lst = new List<int>();
            int Nm = 0;
            for(int i = 0; i < 5000; i++)
            {
                var s = GetTid();
                if (lst.Contains(s))
                {
                    Nm++;
                    Console.WriteLine("重复了"+Nm);
                }
                lst.Add(s);
               
            }

            Console.ReadLine();

        }

 六位数字，5000次数据生产 重复了36次

如何不限定长度，我们的测试如下：

    class Program
    {
        static int seed = 13;
        static ThreadLocal<Random> threadLocal = new ThreadLocal<Random>(() => new Random(Interlocked.Increment(ref seed)));
        public static int GetTid()
        {
            var TxID = Math.Abs(threadLocal.Value.Next() - Convert.ToInt32(DateTime.Now.ToString("HHmmssfff")));
            return TxID;
        }
        public static void Main(string[] args)
        {
            List<int> lst = new List<int>();
            int Nm = 0;
            for(int i = 0; i < 50000; i++)
            {
                var s = GetTid();
                if (lst.Contains(s))
                {
                    Nm++;
                    Console.WriteLine("重复了"+Nm);
                }
                lst.Add(s);
               
            }

            Console.ReadLine();

        }

    }

 50000次仅仅重复了一次

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