| MoreEnumerable | Provides a set of static methods for querying objects that implement IEnumerableT. |
| SequenceException | The exception that is thrown for a sequence that fails a condition. |
| IExtremaEnumerableT | Exposes the enumerator, which supports iteration over a sequence of some extremum property (maximum or minimum) of a specified type. |
| OrderByDirection | Enumeration that defines values representing valid ordering directions for a sequence. |