| ToLookupTKey, TValue(IEnumerableKeyValuePairTKey, TValue) | Creates a ILookupTKey, TElement from a sequence of KeyValuePairTKey, TValue elements. |
| ToLookupTKey, TValue(IEnumerableValueTupleTKey, TValue) | Creates a Lookup from a sequence of tuples of 2 where the first item is the key and the second the value. |
| ToLookupTKey, TValue(IEnumerableKeyValuePairTKey, TValue, IEqualityComparerTKey) | Creates a ILookupTKey, TElement from a sequence of KeyValuePairTKey, TValue elements. An additional parameter specifies a comparer for keys. |
| ToLookupTKey, TValue(IEnumerableValueTupleTKey, TValue, IEqualityComparerTKey) | Creates a Lookup from a sequence of tuples of 2 where the first item is the key and the second the value. An additional parameter specifies a comparer for keys. |