UnificationTroops

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace UnificationTroops
{
    class Program
    {
        static void Main(string[] args)
        {
            Menu menu = new Menu();
            menu.Run();
        }
    }

    class Menu
    {
        private List<Soldier> _southSquad;
        private List<Soldier> _northSquad;

        public Menu()
        {
            _southSquad = new List<Soldier>()
            {
                new Soldier("Bobler"),
                new Soldier("Alex"),
                new Soldier("B.Magnum"),
                new Soldier("Lokar")
            };

            _northSquad = new List<Soldier>()
            {
                new Soldier("Trader"),
                new Soldier("BorWarden"),
                new Soldier("Lukan"),
                new Soldier("Borry")
            };
        }

        public void Run()
        {
            bool isRun = true;

            while (isRun)
            {
                ShowSquad(_southSquad);
                Console.WriteLine();
                ShowSquad(_northSquad);

                Console.WriteLine("\n1)Объединить и вывести солдат\n" +
                    "2)Выход");
                Console.Write("Ввод: ");

                switch (Console.ReadLine())
                {
                    case "1":
                        UniteSquads();
                        break;
                    case "2":
                        isRun = false;
                        break;
                }
            }
        }

        private void UniteSquads()
        {
            var tempNorthSquad = _northSquad.Where(soldier => soldier.Name.StartsWith("B")).ToList();

            foreach (var soldier in tempNorthSquad)
            {
                _northSquad.Remove(soldier);
            }

            _southSquad = _southSquad.Union(tempNorthSquad).ToList();
        }

        private void ShowSquad(List<Soldier> soldiers)
        {
            foreach (var soldier in soldiers)
            {
                Console.WriteLine(soldier.Name);
            }
        }
    }

    class Soldier
    {
        public string Name { get; private set; }

        public Soldier(string name)
        {
            Name = name;
        }
    }
}