ToLookup

[isc30]

A lookup is a 1:many inmutable map (multi-map; each key is mapped to an IQueryable<> of the values with that key).

Proposed definition:

toLookup<TKey extends Indexer, TValue>(
        keySelector: Selector<TOut, TKey>,
        valueSelector: Selector<TOut, TValue>)
        : IDictionary<TKey, IQueryable<TValue>>;

Can be implemented in a very similar way to GroupBy from List class

[mkonicki]

I will take that