WeaponsReport

using System;
using System.Collections.Generic;
using System.Linq;

namespace WeaponsReport
{
    internal class Program
    {
        static void Main()
        {
            SoldierBase soldierBase = new SoldierBase();
            List<Soldier> soldiers = soldierBase.Fill();
            soldierBase.Show(soldiers);

            Console.WriteLine("\n Received data");
            List<Soldier> selectedSoldiers = soldierBase.GetDataset(soldiers);
            soldierBase.Show(selectedSoldiers);
            Console.ReadKey();
        }
    }

    public class SoldierBase
    {
        public List<Soldier> Fill()
        {
            SoldierProvider soldierProvider = new SoldierProvider();

            return soldierProvider.GetSoldiers();
        }

        public void Show(List<Soldier> soldiers)
        {
            foreach (Soldier soldier in soldiers)
            {
                string serviceTime = soldier.ServiceTime != 0 ? soldier.ServiceTime.ToString() : null;
                Console.WriteLine($"{soldier.Rank} {soldier.Name}\t{soldier.Weapon} {serviceTime}");
            }
        }

        public List<Soldier> GetDataset(List<Soldier> soldiers)
        {
            List<Soldier> selectedSoldiers = new List<Soldier>();
            var dataset = soldiers.Select(soldier => (soldier.Name, soldier.Rank));

            foreach (var record in dataset)
            {
                selectedSoldiers.Add(new Soldier(record.Name, record.Rank));
            }

            return selectedSoldiers.ToList();
        }
    }

    public class SoldierProvider
    {
        private readonly List<Soldier> _soldiers;

        public SoldierProvider()
        {
            _soldiers = new List<Soldier>() {
                new Soldier( "Ivanov","private","assault rifle",1),
                new Soldier( "Kuznetsov","private","assault rifle",2),
                new Soldier( "Smirnov","private","assault rifle",1),
                new Soldier( "Popov","private","machine gun",2),
                new Soldier( "Petrov","sergeant","assault rifle",5),
            };
        }

        public List<Soldier> GetSoldiers()
        {
            return _soldiers;
        }
    }

    public class Soldier
    {
        public Soldier(string name, string rank)
        {
            Name = name;
            Rank = rank;
        }

        public Soldier(string name, string rank, string weapon, int serviceTime)
        {
            Name = name;
            Rank = rank;
            Weapon = weapon;
            ServiceTime = serviceTime;
        }

        public string Name { get; private set; }
        public string Rank { get; private set; }
        public string Weapon { get; private set; }
        public int ServiceTime { get; private set; }
    }
}