The best date store & calculation

[Praveen]

DateTime.UtcNow is added as root attribute, 'Modified' of an xml whenever
xml is changed.
Every 5 secs a check is made whether xml is changed or not, by comparing
previous 'Modified' and current 'Modified'.

By considering performance in mind whats best to way of stroring and
calculating date in this case?

Is UtcNow best for comparing every 5 secs.?
Or is it better saving UtcNow.ticks and comparing it.?

How to get UtcNow.ticks in seconds/milliseconds?
UtcNow.ticks gives ticks from Jan 01, 0001. How to get it from another date,
say How to get ticks/milliseconds since jan 01, 1970 (as in case of
Javascript)?
thanks,
Praveen

[Marc Gravell]

>From the computer's perspective, "every 5 seconds" is not very often,
so I would keep it simple and stick with the natural format, DateTime.
Less to go wrong.

For duration between 2 times, use Subtract, which gives you a
TimeSpan. Or simply subtact pre-caculate the ticks of your origin
date, and subtract this from the ticks for now - i.e. (notepad code -
not tested)
long origin = new DateTime(1970,1,1).Ticks; // note this is in local
time, not UTC
....
long ticks = DateTime.Now.Ticks - origin; // so use local time here
also?

Can I ask what the scenario is here? What could change the xml? It is
a file? Something in memory? There may be other ways to monitor for
changes. Size of the xml, and the source (remote database vs in local
memory) makes a difference too.

Marc

[Marc Gravell]

OK - more or less what I suspected; just watch out for thread safety
when accessing the various objects. Web apps are multi-threaded.

Marc