how to select elements that not intersec? [duplicate]

Question

This question already has answers here:

Get the symmetric difference from generic lists (7 answers)

The opposite of Intersect() (8 answers)

Closed 8 years ago.

If I have two list and I want the elements that are common in both lists, I can use this code:

var listC = listA.Intersect(listB);

However, If I want the elements that are not common? And without duplicates? is possible with intersect?

Thanks.

Answer 1

Yep, that's possible. It's called Enumerable.Except.

Use this:

var result = listA.Except(listB); //maybe a .ToList() at the end,
//or passing an IEqualityComparer<T> if you want a different equality comparison.

Answer 2

Neither answer so far will include items from listB that aren't in listA. To get any item that is in either list, but is not in both lists:

listA.Union(listB).Except(listA.Intersect(listB));

Answer 3

Most efficient:

var set = new HashSet<T>(listA);
set.SymmetricExceptWith(listB);