C# - most efficient way of measuring ellapsed time

Question

I am working on a C# console application in which I need to know the ellapsed time since the program has started.
I have a variable that stores the time on start (DateTime now = DateTime.Now;)

What is the most efficient way of measuring the ellapsed time?
The ellapsed time can be hours - this is why I am concerned about efficiency and memory usage.

Thanks in advance!

`var elapsed = DateTime.Now - now;`, this produces a [TimeSpan](https://learn.microsoft.com/en-us/dotnet/api/system.timespan?view=net-5.0), and there is absolutely nothing to be concerned about, the passage of time is very efficient, it 'just happens'. — Peter B, Feb 23 '21 at 12:48
Why all the concern about efficiency here? Are you just trying to be efficient, or is there some particular need you're trying to optimize for? — mason, Feb 23 '21 at 13:53
StopWatch : https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.stopwatch?view=net-5.0. — granadaCoder, Feb 23 '21 at 14:06
This is probably a borderline repeat question. https://stackoverflow.com/questions/55686928/using-stopwatch-in-c-sharp — granadaCoder, Feb 23 '21 at 14:07

trashr0x · Answer 1 · 2021-02-23T15:39:53.640

1

Subtract the current time from the time the program started. This will return a TimeSpan which exposes properties like TotalHours which you can use to calculate the elapsed time.

// on start
var startTime = DateTime.UtcNow;

// later on, to see hours elapsed since then
var elapsed = (DateTime.UtcNow - startTime).TotalHours;

edited Feb 23 '21 at 15:39

answered Feb 23 '21 at 13:50

trashr0x

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adding an explanation is often helpful – con Feb 23 '21 at 14:42

score 0 · Accepted Answer · answered Feb 23 '21 at 12:49

Don't worry. Measuring a time span does not use any resources, as it just compares now with then.

DateTime start = DateTime.Now;

// do some heavy calculation

TimeSpan delta = DateTime.Now - start; // get the time that elapsed

This does not use any resources except the variable for the start, which is just a 64 bit counter.

Note that for short timespans you're better off using Stopwatch, as this is not subject to time adjustments that may happen between start and now.

C# - most efficient way of measuring ellapsed time

2 Answers2