c# - Compare two lists, where order doesn't matter, using IEqualityComparer

Question

I want to check if two lists contain the same items. The order of the items doesn't matter, and the same items might appear twice in each list.

For example:

var List1 = new List<int> { 1, 2, 2 };
var List2 = new List<int> { 2, 1, 2 };
//equal

var List1 = new List<int> { 1, 2, 2 };
var List2 = new List<int> { 2, 1, 1 };
//not equal - different quantities of 1s and 2s in the two lists

Currently I do this as follows:

var List2copy = List2.ToList();
if (List1.Count != List2.Count) return false;
return List1.All(x => List2copy.Remove(x));

Now however I need to use an IEqualityComparer for the two items, which Remove cannot accept. Can anyone think of an efficient solution for the problem? It would also be useful if it accepted an IEnumerable rather than a List

Answer 1

Try this should work for your situation:

return ListA.OrderBy(x => x).SequenceEqual(ListB.OrderBy(x => x));

Just a temporary order then compare