static void Main(string[] args)
        {
            //时间戳转日期
            //var date = Timestamp2Datetime(1576851227);
            var date = Timestamp2Datetime(1576851413790);
            Console.WriteLine(date);
            //日期转时间戳
            //string timestamp = Convert.ToInt32((DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0)).TotalSeconds).ToString();
            string timestamp = Convert.ToInt64((DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0)).TotalMilliseconds).ToString();
            Console.WriteLine(timestamp);

            Console.ReadKey();
        }

        /// <summary>
        /// 时间戳转日期
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static DateTime Timestamp2Datetime(double value)
        {
            System.DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new System.DateTime(1970, 1, 1, 0, 0, 0));
            dtStart = dtStart.AddMilliseconds(value);  //毫秒
            //dtStart = dtStart.AddSeconds(value);  //秒
            return dtStart;
        }

运行结果
图片说明