C# DateTime时间戳帮助类型

https://www.cnblogs.com/minotauros/p/10773258.html

 /// <summary>
    /// 时间工具类
    /// </summary>
    public static class DateTimeUtil
    {
        /// <summary>
        /// 时间戳计时开始时间
        /// </summary>
        private static DateTime timeStampStartTime = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

        /// <summary>
        /// DateTime转换为10位时间戳（单位：秒）
        /// </summary>
        /// <param name="dateTime"> DateTime</param>
        /// <returns>10位时间戳（单位：秒）</returns>
        public static long DateTimeToTimeStamp(DateTime dateTime)
        {
            return (long)(dateTime.ToUniversalTime() - timeStampStartTime).TotalSeconds;
        }

        /// <summary>
        /// DateTime转换为13位时间戳（单位：毫秒）
        /// </summary>
        /// <param name="dateTime"> DateTime</param>
        /// <returns>13位时间戳（单位：毫秒）</returns>
        public static long DateTimeToLongTimeStamp(DateTime dateTime)
        {
            return (long)(dateTime.ToUniversalTime() - timeStampStartTime).TotalMilliseconds;
        }

        /// <summary>
        /// 10位时间戳（单位：秒）转换为DateTime
        /// </summary>
        /// <param name="timeStamp">10位时间戳（单位：秒）</param>
        /// <returns>DateTime</returns>
        public static DateTime TimeStampToDateTime(long timeStamp)
        {
            return timeStampStartTime.AddSeconds(timeStamp).ToLocalTime();
        }

        /// <summary>
        /// 13位时间戳（单位：毫秒）转换为DateTime
        /// </summary>
        /// <param name="longTimeStamp">13位时间戳（单位：毫秒）</param>
        /// <returns>DateTime</returns>
        public static DateTime LongTimeStampToDateTime(long longTimeStamp)
        {
            return timeStampStartTime.AddMilliseconds(longTimeStamp).ToLocalTime();
        }
    }