Question

I have two IList<Traffic> I need to combine.

Traffic is a simple class:

class Traffic
{
  long MegaBits;
  DateTime Time;
}

Each IList holds the same Times, and I need a single IList<Traffic>, where I have summed up the MegaBits, but kept the Time as key.

Is this possible using Linq ?

EDIT:

I forgot to mention that Time isn’t necessarily unique in any list, multiple Traffic instances may have the same Time.

Also I might run into X lists (more than 2), I should had mentioned that as well – sorry 🙁

EXAMPLE:

IEnumerable<IList<Traffic>> trafficFromDifferentNics;

var combinedTraffic = trafficFromDifferentNics
                        .SelectMany(list => list)
                        .GroupBy(traffic => traffic.Time)
                        .Select(grp => new Traffic { Time = grp.Key, MegaBits = grp.Sum(tmp => tmp.MegaBits) });

The example above works, so thanks for your inputs 🙂

Answer 1

You could combine the items in both lists into a single set, then group on the key to get the sum before transforming back into a new set of Traffic instances.

var result = firstList.Concat(secondList)
    .GroupBy(trf => trf.Time, trf => trf.MegaBits)
    .Select(grp => new Traffic { Time = grp.Key, MegaBits = grp.Sum()});