ILookup vs. IGrouping

by

Yes, all of those are correct.

And ILookup<TKey, TValue> also extends IEnumerable<IGrouping<TKey, TValue>> so you can iterate over all the key/collection pairs as well as (or instead of) just looking up particular keys.

I basically think of ILookup<TKey,TValue> as being like IDictionary<TKey, IEnumerable<TValue>>.

Bear in mind that ToLookup is a “do it now” operation (immediate execution) whereas a GroupBy is deferred. As it happens, with the way that “pull LINQ” works, when you start pulling IGroupings from the result of a GroupBy, it has to read all the data anyway (because you can’t switch group midway through) whereas in other implementations it may be able to produce a streaming result. (It does in Push LINQ; I would expect LINQ to Events to be the same.)

More Related Contents:

  1. Group by in LINQ
  2. Group By Multiple Columns
  3. LINQ with groupby and count
  4. C# Linq Group By on multiple columns [duplicate]
  5. LINQ Grouping dynamically
  6. How to get values from IGrouping
  7. Client side GroupBy is not supported
  8. LINQ: combining join and group by
  9. Linq order by, group by and order by each group?
  10. LINQ Group By Multiple fields -Syntax help
  11. linq distinct or group by multiple properties
  12. Group by variable integer range using Linq
  13. LINQ to Entities group-by failure using .date
  14. How to read lines to dictionary with linQ [closed]
  15. Using LINQ to remove elements from a List
  16. Extension methods must be defined in a non-generic static class
  17. Dynamically access table in EF Core 2.0
  18. How to return anonymous type from c# method that uses LINQ to SQL [duplicate]
  19. Get an IDataReader from a typed List
  20. How do I take the Cartesian join of two lists in c#?
  21. LINQ query to find if items in a list are contained in another list
  22. lambda expressions in immediate window for VS2015
  23. Can I LINQ a JSON?
  24. Local variable and expression trees
  25. List complex sorting
  26. Good way to get the key of the highest value of a Dictionary in C#
  27. How to sort a dictionary by key
  28. How to set property value using Expressions? [duplicate]
  29. Is Injection Possible through Dynamic LINQ?
  30. Can I use Linq’s Except() with a lambda expression comparer?

Leave a Comment