How to get elements from collection A that not in collection B? i.e. A-B

Question

Possible Duplicate:
Disjoint Union in LINQ

DUPE: Disjoint Union in LINQ

I know this is a simple collection operation,My code is:

var gone = from a in A
     where B.Contains(a) == false
     select a;

but it not work.

Answer 1

var gone = A.Except(B);