从1970年1月1日00:00:00 GMT以来此时间对象表示的毫秒数转化为Datetime

   /// <summary>
        /// 将Long类型转换为DateTime类型
        /// </summary>
        /// <param name="d">long</param>
        /// <returns></returns>
        public static DateTime ConvertLongDateTime(long ticks)
        {
            DateTime dtBase = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
            DateTime convertTime = dtBase.Add(new TimeSpan(ticks * TimeSpan.TicksPerMillisecond)).ToLocalTime();
            return convertTime;
        }

        /// <summary>
        /// 将DateTime类型转换为long类型
        /// </summary>
        /// <param name="dt">时间</param>
        /// <returns></returns>
        public static long ConvertDataTimeLong(DateTime dt)
        {
            DateTime dtBase = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
            TimeSpan toNow = DateTime.Now.Subtract(dtBase);
            long timeStamp = toNow.Ticks;
            return timeStamp;
        }