PartialOrderBy extension method over IEnumerable<T>

PosetEnumerableExtensions.cs

    public static class EnumerableExtensions
    {
        public static IEnumerable<TSource> PartialOrderBy<TSource, TKey>(this IEnumerable<TSource> source,
                                                                         Func<TSource, TKey> keySelector,
                                                                         IComparer<TKey> comparer)
        {
            var list = new List<TSource>(source);
            while (list.Count > 0)
            {
                var minimum = default(TSource);
                var minimumKey = default(TKey);
                foreach (TSource s in list)
                {
                    TKey k = keySelector(s);
                    minimum = s;
                    minimumKey = k;
                    break;
                }
                foreach (TSource s in list)
                {
                    TKey k = keySelector(s);
                    if (comparer.Compare(k, minimumKey) < 0)
                    {
                        minimum = s;
                        minimumKey = k;
                    }
                }
                yield return minimum;
                list.Remove(minimum);
            }
            yield break;
        }
    }