| TrySingleT, TCardinality(IEnumerableT, TCardinality, TCardinality, TCardinality) | Returns a tuple with the cardinality of the sequence and the single element in the sequence if it contains exactly one element. similar to SingleTSource(IEnumerableTSource). |
| TrySingleT, TCardinality, TResult(IEnumerableT, TCardinality, TCardinality, TCardinality, FuncTCardinality, T, TResult) | Returns a result projected from the the cardinality of the sequence and the single element in the sequence if it contains exactly one element. |