Get the symmetric difference from generic lists

Question

I have 2 separate List and I need to compare the two and get everything but the intersection of the two lists. How can I do this (C#)?

Answer 1

You can use Except to get everything but the intersection of the two lists.

var differences = listA.Except(listB).Union(listB.Except(listA));

If you want to get everything but the union:

var allButUnion = new List<MyClass>();

(The union is everything in both lists - everything but the union is the empty set...)

Answer 2

Do you mean everything that's only in one list or the other? How about:

var allButIntersection = a.Union(b).Except(a.Intersect(b));

That's likely to be somewhat inefficient, but it fairly simply indicates what you mean (assuming I've interpreted you correctly, of course).

Answer 3

Use Except:

List<int> l1 = new List<int>(new[] { 1, 2, 3, 4 });
List<int> l2 = new List<int>(new[] { 2, 4 });
var l3 = l1.Except(l2);

Answer 4

If you mean the set of everything but the intersection (symmetric difference) you can try:

var set = new HashSet<Type>(list1);
set.SymmetricExceptWith(list2);

Answer 5

var theUnion = list1.Concat(list2);
var theIntersection = list1.Intersect(list2);
var theSymmetricDifference = theUnion.Except(theIntersection);

Answer 6

Something like this?

String[] one = new String[] { "Merry", "Metal", "Median", "Medium", "Malfunction", "Mean", "Measure", "Melt", "Merit", "Metaphysical", "Mental", "Menial", "Mend", "Find" };
            String[] two = new String[] { "Merry", "Metal", "Find", "Puncture", "Revise", "Clamp", "Menial" };

List<String> tmp = one.Except(two).ToList();
tmp.AddRange(two.Except(one));

String[] result = tmp.ToArray();