public static long GetTimeSpan(string part, DateTime dateTime1, DateTime dateTime2)
{
long now = DateTime.Now.Ticks;
long begin = DateTime.Parse("2000-1-1 0:0:0").Ticks;
long timeSpan = (long)Math.Abs(now - begin);
switch(part.ToLower())
{
case "f":
timeSpan = timeSpan / TimeSpan.TicksPerMillisecond;
break;
case "s":
timeSpan = timeSpan / TimeSpan.TicksPerSecond;
break;
case "m":
timeSpan = timeSpan / TimeSpan.TicksPerMinute;
break;
case "h":
timeSpan = timeSpan / TimeSpan.TicksPerHour;
break;
case "d":
timeSpan = timeSpan / TimeSpan.TicksPerDay;
break;
default:
timeSpan = 0;
break;
}