Median

Median.cs

double Median<TSource>(this IEnumerable<TSource> source, Func<TSource, int> selector)
{
    if (!source.Any()) throw new InvalidOperationException();

    var sorted = source.OrderBy(selector);

    var count = (int)(sorted.Count());

    int index = count / 2;

    if (count % 2 == 0)
    {
        return new [] { selector(sorted.ElementAt(index)), selector(sorted.ElementAt(index - 1)) }.Average();
    }
    else
    {
        return selector(sorted.ElementAt(index));
    }
}