Question

If I have an

IEnumerable<Something>

and a function that takes a Something, and return an int, how would I use LINQ to tell me which of my somethings gives the highest result when fed to my function?

Answer 1

You can use something like MaxBy from MoreLinq (or simply use MoreLinq):

public static TSource MaxBy<TSource, TKey>(this IEnumerable<TSource> source,
    Func<TSource, TKey> selector, IComparer<TKey> comparer)
{
    using (IEnumerator<TSource> sourceIterator = source.GetEnumerator())
    {
        if (!sourceIterator.MoveNext())
            throw new InvalidOperationException("Sequence was empty");
        TSource max = sourceIterator.Current;
        TKey maxKey = selector(max);

        while (sourceIterator.MoveNext())
        {
            TSource candidate = sourceIterator.Current;
            TKey candidateProjected = selector(candidate);
            if (comparer.Compare(candidateProjected, maxKey) > 0)
            {
                max = candidate;
                maxKey = candidateProjected;
            }
        }
        return max;
    }
}