c#日期和时间戳互转

using System;
using System.Collections.Generic;
using System.Data;
using System.Reflection;

namespace Common
{
    public static class ExtendMethod
    {
        // DateTime --> long
        public static long? ConvertDataTimeToLong(this DateTime? dt)
        {
            if (dt == null || dt == default(DateTime)) return null;
            try
            {
                DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(, , ));
                TimeSpan toNow = dt.Value.Subtract(dtStart);
                long timeStamp = toNow.Ticks;
                timeStamp = long.Parse(timeStamp.ToString().Substring(, timeStamp.ToString().Length - ));
                return timeStamp <=  ?  : timeStamp;
            }
            catch
            {
                return null;
            }
        }

        // long --> DateTime
        public static DateTime? ConvertLongToDateTime(this long? d)
        {
            if (d == ) return null;
            try
            {
                DateTime dtStart = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(, , ));
                long lTime = long.Parse(d + "");
                TimeSpan toNow = new TimeSpan(lTime);
                DateTime dtResult = dtStart.Add(toNow);
                return dtResult;
            }
            catch
            {
                return null;
            }
        }
    }
}