Finding the difference between two lists of strings

Question

I\'m pretty sure this is a duplicate, but I have tried everything, and I still cannot seem to get the differences. I have two lists of strings: listA and listB. I\'m trying to

Answer 1

listA.Except(listB).ToList();

should give the correct answer, but

set.SymmetricExceptWith(listB);

should not. SymmetricExcept will give the items in listA not in listB plus the items in ListB not in ListA.