Selecting items from list A which are not in List B and vice versa

Question

I have two list of A and B and trying to get elements from A which are not in B and from B which are not in A.

Below is my attempt to solve this.

var result = (List<string>)(from e in (A.Concat(B))
where !B.Contains(e) || !A.Contains(e)
select e);

And ran into below error..

Unable to cast object of type WhereEnumerableIterator1[System.String] to type System.Collections.Generic.List`1[System.String].

What can I try to solve this?

Add `.ToList()` after your query to tell the query to convert the result into a list. You also don't need the `List` cast — ShuberFu, May 24 '16 at 18:58
I marked it as a duplicate even though yours works if you either cal `ToList` or remove the cast to `List` — D Stanley, May 24 '16 at 19:09

Salah Akbari · Answer 1 · 2016-05-24T19:15:31.723

3

You can use Except:

List<int> firstList = new List<int> {1,2,3,4};

List<int> secondList = new List<int> { 1, 5 };

IEnumerable<int> res = secondList.Except(firstList).Concat(firstList.Except(secondList));

//Result => {5,2,3,4}

edited May 24 '16 at 19:15

answered May 24 '16 at 18:59

Salah Akbari

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Just tried to solve this, saw S.Akbari's solution, tried it. It worked +1 – mark_h May 24 '16 at 19:05

score 1 · Accepted Answer · edited May 24 '16 at 19:02

1

Regarding you cast error, the call should be like this.

var result = (from e in (A.Concat(B))
              where !B.Contains(e) || !A.Contains(e)
              select e).ToList();`

The ToList() method converts your LINQ query into a list.

edited May 24 '16 at 19:02

Jonesopolis

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answered May 24 '16 at 19:01

ShuberFu

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Hmm.. My bad. Thanks :) – BetterLateThanNever May 24 '16 at 19:03

Selecting items from list A which are not in List B and vice versa

2 Answers2