How do I do an integer list intersection while keeping duplicates?

Question

I\'m working on a Greatest Common Factor and Least Common Multiple assignment and I have to list the common factors. Intersection() won\'t work because that removes duplicat

Answer 1

Here's one way to do it. To be fair, it is very similar to David B's answer except that it uses a join to do the association.

IEnumerable seqA = ...
IEnumerable seqB = ...

var result = from aGroup in seqA.GroupBy(x => x)
             join bGroup in seqB.GroupBy(x => x) 
                         on aGroup.Key equals bGroup.Key
             let smallerGroup = aGroup.Count() < bGroup.Count() 
                                ? aGroup : bGroup
             from item in smallerGroup
             select item;