Short example of MemoryCache

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Caching;

namespace CacheTest
{
    internal class Program
    {
        private UnitRepo _unitrepo;

        private static void Main()
        {
            new Program().Run();
        }

        private void Run()
        {
            _unitrepo = new UnitRepo();

            Console.WriteLine("Getting Unit 3");
            var unit = GetUnitFromRepo(3);
            Console.WriteLine($"Got Unit '{unit.Name}'");

            Console.WriteLine("Getting Unit 4");
            unit = GetUnitFromRepo(4);
            Console.WriteLine($"Got Unit '{unit.Name}'");

            Console.WriteLine("Getting Unit 3");
            unit = GetUnitFromRepo(3);
            Console.WriteLine($"Got Unit '{unit.Name}'");

            Console.WriteLine("Getting Unit 4");
            unit = GetUnitFromRepo(4);
            Console.WriteLine($"Got Unit '{unit.Name}'");

            Console.ReadLine();
        }

        private Unit GetUnitFromRepo(int id)
        {
            var cache = MemoryCache.Default;

            var unit = (Unit) cache[id.ToString()];

            if (unit == null)
            {
                unit = _unitrepo.GetUnitById(id);

                cache.Add(id.ToString(), unit, new CacheItemPolicy());
            }

            return unit;
        }
    }

    internal class Unit
    {
        public Unit(int id)
        {
            Id = id;
        }

        public string Name => Id.ToString();

        public int Id { get; }
    }

    internal class UnitRepo
    {
        public UnitRepo()
        {
            Units = new List<Unit>();

            for (var i = 0; i < 10; i++)
                Units.Add(new Unit(i));
        }

        public IList<Unit> Units { get; }

        public Unit GetUnitById(int id)
        {
            Console.WriteLine("Gotten from UnitRepo");
            return Units.Single(x => x.Id == id);
        }
    }
}