Get "Value" property in IGrouping

Question

I have a data structure like

public DespatchGroup(DateTime despatchDate, List<Products> products);

And I am trying to do...

var list = new List<DespatchGroup>();

foreach (var group in dc.GetDespatchedProducts().GroupBy(i => i.DespatchDate))
{
    // group.Values is not correct... how do I write this?
    list.Add(new DespatchGroup(group.Key, group.Values);
}

I'm obviously not understanding IGrouping as I can't see how to actually get to the data records within the group!

The edit [(Rev2)](http://stackoverflow.com/revisions/4804477/2) wasn't very constructive as it doesn't match any of the answers. — Sunny Patel, May 14 '14 at 17:30

score 217 · Accepted Answer · answered Jan 26 '11 at 12:23

217

The group implements IEnumerable<T> - In the general case, just call foreach over the group. In this case, since you need a List<T>:

list.Add(new DespatchGroup(group.Key, group.ToList());

answered Jan 26 '11 at 12:23

Marc Gravell

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So basically if we are following the essence of the question `value` is comparable to `ToList()` only there is more of an overhead there to convert it to a list as opposed to just pulling out a value – Paul C Dec 17 '14 at 15:25
2

@CodeBlend there's more overhead because they want a list. If there was a `Values` property like they imagined then they'd have to do `group.Values.ToList()`. Conversely if they accepted any enumerable instead of a list then `new DespatchGroup(group.Key, group)` would work. The overhead is from the definition of `DespachGroup` not from the way IGrouping works. – Jon Hanna Jun 19 '15 at 10:18

score 45 · Answer 2 · answered Jan 26 '11 at 12:23

45

There's no Values property or similar because the IGrouping<T> itself is the IEnumerable<T> sequence of values. All you need to do in this case is convert that sequence to a list:

list.Add(new DespatchGroup(group.Key, group.ToList());

answered Jan 26 '11 at 12:23

LukeH

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We may also convert to an IEnumerable if we wish: `group.AsEnumerable()`. – Mateen Ulhaq Jan 28 '16 at 18:55
@MateenUlhaq While that is possible it is a bit redundant as IGrouping already is derived from IEnumerable. It will work in most places you would use IEnumerable without needing any kind of explicit casting/converting. – Leon Lucardie Jun 15 '21 at 15:19

score 41 · Answer 3 · edited Nov 30 '15 at 16:01

41

For any selected group,you could call

var selectedGroupValues=selectedGroup.SelectMany(x=>x);

edited Nov 30 '15 at 16:01

Andy

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answered Nov 30 '15 at 15:52

Bassl Kokash

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Thanks! Unlike `.Select` which will return an IGrouping<> again, `.SelectMany` will return an IEnumerable of the groupped values' type, which is what I was after. – K0D4 Oct 01 '18 at 18:53
I'd say only use this when there are (potentially) multiple groups selected. (aka `IEnumerable>`). Otherwise, use `toList()`, or simply cast it to `IEnumerable`. – apple apple Jan 09 '20 at 05:33

score 27 · Answer 4 · answered Oct 22 '12 at 19:34

27

Just a related tip - since, as the other answers have said, the grouping is an IEnumerable, if you need to access a specific index you can use group.ElementAt(i).

This is probably obvious to a lot of people but hopefully it will help a few!

answered Oct 22 '12 at 19:34

Rob H

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Get "Value" property in IGrouping

4 Answers4