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 combine Concat and Distinct to do this:

foo = foo.Concat(accessories).Distinct().ToList();

Edit: Or Except as others have pointed out, which seems to be the superior choice for this case.

Answer 2

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<string> foo = foo.Union(accessories).ToList();

Answer 3

There's a LINQ method to do this for you, it looks like this; accessories.Except(foo);

Answer 4

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();

Answer 5

Use List.Except:

foo.AddRange(accessories.Except(foo));

From MSDN:

Except Produces the set difference of two sequences.