C# 時間戳與DateTime間的互相轉換

//DateTime轉換為時間戳
public long GetTimeSpan(DateTime time)
{
      DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970,1,1,0,0,0,0));  
　　　 return (long)(time - startTime).TotalSeconds;
}
//timeSpan轉換為DateTime
public DateTime TimeSpanToDateTime(long span)
{
　　DateTime time = DateTime.MinValue;
   DateTime startTime = TimeZone.CurrentTimeZone.ToLocalTime(new DateTime(1970,1,1,0,0,0,0)); 
　　time=startTime.AddSeconds(span);
　　return time;

}