Edit Question - KnowledgeHub

Title Body

I've been having trouble articulating the differences between ILookup<TKey, TVal> and IGrouping<TKey, TVal> , and am curious if I understand it correctly now. LINQ compounded the issue by producing sequences of IGrouping items while also giving me a ToLookup extension method. So it felt like they were the same until I looked more closely. var q1 = from n in N group n by n.MyKey into g select g; // q1 is IEnumerable<IGrouping<TKey, TVal>> Which is equivalent to: var q2 = N.GroupBy(n => n.MyKey, n => n); // q2 is IEnumerable<IGrouping<TKey, TVal>> Which looks a lot like: var q3 = N.ToLookup(n => n.MyKey, n => n); // q3 is ILookup<TKey, TVal> Am I correct in the following analogies? An IGrouping<TKey, TVal> is a single group (i.e. a keyed sequence), analogous to KeyValuePair<TKey, TVal> where the value is actually a sequence of elements (rather than a single element) An IEnumerable<IGrouping<TKey, TVal>> is a sequence of those (similar to what you get when iterating over an IDictionary<TKey, TVal> An ILookup<TKey, TVal> is more like a IDictionary<TKey, TVal> where the value is actually a sequence of elements

Tags (comma-separated) Cancel