using System; using System.Collections.Generic; using System.Linq; namespace NzbDrone.Common { public static class IEnumerableExtensions { public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) { var knownKeys = new HashSet<TKey>(); return source.Where(element => knownKeys.Add(keySelector(element))); } } }