Sum of TimeSpans in C#

Question

I have a collection of objects that include a TimeSpan variable:

MyObject {      TimeSpan TheDuration { get; set; } } 

I want to use LINQ to sum those times. Of course, (from r in MyCollection select r.TheDuration).Sum(); doesn't work!

I'm thinking of changing the datatype of TheDuration to an int and then summing it and converting the sum to a TimeSpan. That will be messy because each TheDuration in my collection is used in as a timespan somewhere else.

Any suggestion on this summation?

Answer 1

Unfortunately, there isn't a an overload of Sum that accepts an IEnumerable<TimeSpan>. Additionally, there's no current way of specifying operator-based generic constraints for type-parameters, so even though TimeSpan is "natively" summable, that fact can't be picked up easily by generic code.

One option would be to, as you say, sum up an integral-type equivalent to the timespan instead, and then turn that sum into a TimeSpan again. The ideal property for this is TimeSpan.Ticks, which round-trips accurately. But it's not necessary to change the property-type on your class at all; you can just project:

var totalSpan = new TimeSpan(myCollection.Sum(r => r.TheDuration.Ticks)); 

Alternatively, if you want to stick to the TimeSpan's + operator to do the summing, you can use the Aggregate operator:

var totalSpan = myCollection.Aggregate                 (TimeSpan.Zero,                  (sumSoFar, nextMyObject) => sumSoFar + nextMyObject.TheDuration); 

Answer 2

This works well (code based on Ani's answer)

public static class StatisticExtensions {         public static TimeSpan Sum<TSource>(this IEnumerable<TSource> source, Func<TSource, TimeSpan> selector)     {         return source.Select(selector).Aggregate(TimeSpan.Zero, (t1, t2) => t1 + t2);     } } 

Usage :

If Periods is a list of objects with a Duration property

TimeSpan total = Periods.Sum(s => s.Duration)