using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
var list1 = new List<string> { "item1", "item2" };
var list2 = new List<string> { "item2", "item3" };
var unionResult = list1.Union(list2);
Console.WriteLine(string.Join(", ", unionResult));
}