唯一性ID生成器：

using System;
using System.Collections.Generic;
using System.Text;

namespace Test.Core
{
    /// <summary>
    /// 唯一性ID生成器
    /// </summary>
    public class SFID
    {

        /// <summary>
        /// 初始基准时间戳，小于当前时间点即可
        /// 分布式项目请保持此时间戳一致
        /// </summary>
        private static long _twepoch = 0L;

        /// <summary>
        /// 毫秒计数器
        /// </summary>
        private static long sequence = 0L;

        /// <summary>
        /// 最大机器ID所占的位数
        /// </summary>
        private static long maxWorkerId = 90;

        /// <summary>
        /// 一微秒内可以产生计数，如果达到该值则等到下一微妙在进行生成
        /// </summary>
        private static long sequenceMask = 99;

        /// <summary>
        /// 最后一次的时间戳
        /// </summary>
        private static long lastTimestamp = -1L;

        /// <summary>
        /// 线程锁对象
        /// </summary>
        private static object locker = new object();

        /// <summary>
        /// 机器码
        /// </summary>
        private static long _workerId = 99;

        /// <summary>
        /// 机器编号
        /// </summary>
        public static long WorkerID
        {
            get { return _workerId; }
            set
            {
                if (value >= 0 && value < maxWorkerId)
                    _workerId = value;
                else
                    throw new Exception($"机器码必须在0至{ maxWorkerId}之间");
            }
        }
        /// <summary>
        /// 获取多个集合
        /// </summary>
        /// <param name="totalCount"></param>
        /// <returns></returns>
        public static IEnumerable<long> NewID(int totalCount)
        {
            for (var i = 0; i < totalCount; i++)
            {
                yield return NewID();
            }
        }
        /// <summary>
        /// 机器编码的基数 
        /// </summary>
        private static long _workerBasic = 10000000000000L;

        /// <summary>
        /// 获取新的ID
        /// </summary>
        /// <returns></returns>
        public static long NewID()
        {
            lock (locker)
            {
                //WorkerID = workId;
                long timestamp = timeGen();
                if (lastTimestamp == timestamp)
                { //同一微妙中生成ID
                    sequence++; //用&运算计算该微秒内产生的计数是否已经到达上限
                    if (sequence > sequenceMask)
                    {
                        //一微妙内产生的ID计数已达上限，等待下一微妙
                        timestamp = tillNextMillis(lastTimestamp);
                    }
                }
                else
                { //不同微秒生成ID
                    sequence = 0; //计数清0
                }
                if (timestamp < lastTimestamp)
                {
                    //如果当前时间戳比上一次生成ID时时间戳还小，抛出异常，因为不能保证现在生成的ID之前没有生成过
                    throw new Exception($"Clock moved backwards.  Refusing to generate id for {lastTimestamp - timestamp} milliseconds");
                }
                lastTimestamp = timestamp; //把当前时间戳保存为最后生成ID的时间戳

                return WorkerID * _workerBasic + lastTimestamp * 100 + sequence;
            }
        }

        ///// <summary>
        ///// 获取新的ID
        ///// </summary>
        ///// <param name="workId"></param>
        ///// <returns></returns>
        //public static long NewID(int workId)
        //{
        //    WorkerID = workId;
        //    return NewID();
        //}


        /// <summary>
        /// 获取下一微秒时间戳
        /// </summary>
        /// <param name="lastTimestamp"></param>
        /// <returns></returns>
        private static long tillNextMillis(long lastTimestamp)
        {
            long timestamp = timeGen();
            while (timestamp <= lastTimestamp)
            {
                timestamp = timeGen();
            }
            sequence = 0;
            return timestamp;
        }

        private static DateTime _date = new DateTime(2019, 1, 1, 0, 0, 0, DateTimeKind.Utc);
        /// <summary>
        /// 当前时间戳
        /// </summary>
        /// <returns></returns>
        private static long timeGen()
        {
            return (long)(DateTime.UtcNow - _date).TotalMilliseconds;
        }


    }
}

调用：

long ID = SFID.NewID();