using System;

using System.Collections.Generic;

using System.Linq;

​

namespace ConsoleApp1

{

    public class MyKey

    {

        public string Code { get; }

​

        public MyKey(string code) => Code = code ?? throw new ArgumentNullException("code");

​

        public override int GetHashCode() => Code.GetHashCode();

    }

​

    public class Program

    {

        public static void Main1(string[] args)

        {

            var myMap = new Dictionary<MyKey, string>();

​

            var key = new MyKey("KeyA");

            myMap.Add(key, "Value1");

​

            key = new MyKey("KeyB");

            myMap.Add(key, "Value2");

            myMap[key] = "Value3";

​

            key = new MyKey("KeyA");

            myMap[key] = "Value3";

​

            myMap.Remove(new MyKey("KeyB"));

            Console.WriteLine($"size = {myMap.Count}");

            //Console.WriteLine($"dictionary: {myMap.Aggregate(string.Empty, (s, pair) => s + $"{pair.Key.Code}:{pair.Value} ")}");

        }

    }

}