List<Person> distinctPeople = allPeople .GroupBy(p => new {p.PersonId, p.FavoriteColor} ) .Select(g => g.First()) .ToList();
public static IEnumerable<TSource> DistinctBy<TSource, TKey> (this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) { HashSet<TKey> seenKeys = new HashSet<TKey>(); foreach (TSource element in source) { if (seenKeys.Add(keySelector(element))) { yield return element; } } }