| DistinctByTSource, TKey(IEnumerableTSource, FuncTSource, TKey) | Returns all distinct elements of the given source, where "distinctness" is determined via a projection and the default equality comparer for the projected type. |
| DistinctByTSource, TKey(IEnumerableTSource, FuncTSource, TKey, IEqualityComparerTKey) | Returns all distinct elements of the given source, where "distinctness" is determined via a projection and the specified comparer for the projected type. |