Add elements from one list to another C#

Question

What is the simplest way to add elements of one list to another?

For example, I have two lists:

List A which contains x items List B which contains y items.

Answer 1

To join two lists, you can do

listA.AddRange(listB); // listA will contain x+y items

or

// listC contains x+y items, listA and listB are unchanged.
var listC = listA.Concat(listB); 

You could use the latter to reassign listA instead:

listA = listA.Concat(listB).ToList();

but there isn't any particular advantage to that over AddRange if you're okay with modifying one of the original lists in the first place.