using Linq, you can remove duplication in a NAME_1 by using the Distinct() method. For example, NAME_2 = new NAME_1 { "a", "b", "c", "a" };
NAME_2.RemoveAll(NAME_2.Contains);
NAME_2.RemoveAll(NAME_2.Equals);
NAME_2.Distinct().ToList(); // Output: "a", "b", "c"