LINQ Comparing two list and putting the results into one list

Question

I have a C# application. I have two lists ('NewStock' and 'OldStock') of the same custom type, 'Book'. I want to extract any 'Book' object that is the list NewStock but not in the OldStock list into a new list called ResultList. Please see an example below. How do I do this?

I have used implemented the IEqualityComparer interface on my class Book so that I check if a book object is equal to another.

 NewStock      OldStock
 A             A
 B             C
 C            
 D

Result I would like,

ResultList
B
D

`var results = newStock.Except(oldStock).ToList()` and you can provide a custom comparer to `Except` to do this. — Adam Houldsworth, Apr 04 '14 at 13:26
Maybe related: http://stackoverflow.com/questions/3944803/use-linq-to-get-items-in-one-list-that-are-not-in-another-list — bkardol, Apr 04 '14 at 13:27
@NathanKoop Done, though I expect this to be closed as a duplicate. These usually are. — Adam Houldsworth, Apr 04 '14 at 13:27

score 4 · Accepted Answer · answered Apr 04 '14 at 13:27

4

var results = newStock.Except(oldStock).ToList()

And you can provide a custom comparer to Except to do this.

answered Apr 04 '14 at 13:27

Adam Houldsworth

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score 2 · Answer 2 · answered Apr 04 '14 at 13:27

2

Use except to do this:

Example can be found here: MSDN

answered Apr 04 '14 at 13:27

Henrik

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score 1 · Answer 3 · answered Apr 04 '14 at 13:26

1

Try this one:

List<Book> ResultList = NewStock.Select(x=>!OldStock.Contains(x)).ToList();

answered Apr 04 '14 at 13:26

Christos

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LINQ Comparing two list and putting the results into one list

3 Answers3