Using Linq Except not Working as I Thought

Question

List1 contains items { A, B } and List2 contains items { A, B, C }.

What I need is to be returned { C }

Answer 1

If you are storing reference types in your list, you have to make sure there is a way to compare the objects for equality. Otherwise they will be checked by comparing if they refer to same address.

You can implement IEqualityComparer and send it as a parameter to Except() function. Here's a blog post you may find helpful.

edit: the original blog post link was broken and has been replaced above