Fastest way to find common items across multiple lists in C#

Question

Given the following:

List> optionLists;

what would be a quick way to determine the subset of Option objects that a

Answer 1

Ok, this will find the list of Option objects that have a Value appearing in every list.

var x = from list in optionLists
        from option in list
        where optionLists.All(l => l.Any(o => o.Value == option.Value))
        orderby option.Value
        select option;

It doesn't do a "distinct" select so it'll return multiple Option objects, some of them with the same Value.