NewHw28

using System;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        List<int> list1 = new List<int> { 1, 5, 3, 7, 6, 8 };
        List<int> list2 = new List<int> { 2, 4, 3, 8 };

        List<int> targetList = UniteLists(list1, list2);

        foreach (var item in targetList)
        {
            Console.Write($"{item}, ");
        }

        Console.ReadKey();
    }

    static List<int> UniteLists(List<int> list, List<int> subList)
    {
        List<int> targetList = new List<int>();

        for (int i = 0; i < list.Count; i++)
        {
            for (int j = 0; j < subList.Count; j++)
            {
                if(list[i] == subList[j])
                {
                    subList.Remove(subList[j]);
                }
            }
        }

        list.AddRange(subList);

        targetList = list;
        targetList.Sort();

        return targetList;
    }
}