How to compare 2 List objects to get the missing value from the List

Question

How do I use the \"NOT IN\" to get the missing data, to be added to \"foo\" List.

var accessories = new List(); 
var foo = new List()         


        

Answer 1

You can use .Except() to get the difference between two sets:

var difference = accessories.Except(foo);
// difference is now a collection containing elements in accessories that are not in foo

If you then want to add those items to foo:

foo = foo.Concat(difference).ToList();