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

If you just want foo to be the distinct combination of all elements in foo and accessories (i.e., the union of the two lists),

List foo = foo.Union(accessories).ToList();