using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;

namespace Test1
{
    class A {
        public string text;
    }

    class B : A {
    }

    class C : A {
        public override bool Equals(object other)
        {
            return text==(other as C).text;
        }
        public override int GetHashCode()
        {
            return text.GetHashCode();
        }
    }

    class Program
    {
        private static Random random = new Random();
        public static string RandomString(int length)
        {
            const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
            return new string(Enumerable.Repeat(chars, length)
              .Select(s => s[random.Next(s.Length)]).ToArray());
        }

        static void benchmark<T, N>(string label, List<T> listYes, List<N> listNo) where T : A where N: A{
            int ticks = Environment.TickCount;

            for (int i = 0; i < 1000; i++)
            {
                Dictionary<A, int> dict = new Dictionary<A, int>();

                foreach (T t in listYes)
                {
                    dict.Add(t, 1);
                }

                foreach (N t in listNo)
                {
                    if (dict.ContainsKey(t)) throw new Exception("oops!");
                }

                foreach (T t in listYes)
                {
                    if (!dict.ContainsKey(t)) throw new Exception("oops!");
                }
            }

            Console.WriteLine(label+" took "+(Environment.TickCount-ticks) + "ms");
        }

        static void Main(string[] args)
        {
            Console.WriteLine("B{'xxx'}.HashCode = " + new B { text = "xxx" }.GetHashCode());
            Console.WriteLine("B{'xxx'}.HashCode = " + new B { text = "xxx" }.GetHashCode());
            Console.WriteLine("C{'xxx'}.HashCode = " + new C { text = "xxx" }.GetHashCode());
            Console.WriteLine("C{'xxx'}.HashCode = " + new C { text = "xxx" }.GetHashCode());

            List<string> items = new List<string>();
            for (int i = 0; i < 10000; i++) items.Add(RandomString(10));

            List<B> itemsB = new List<B>();
            foreach (string item in items) itemsB.Add(new B { text = item });

            List<C> itemsC = new List<C>();
            foreach (string item in items) itemsC.Add(new C { text = item });

            benchmark("B", itemsB, itemsC);
            benchmark("C", itemsC, itemsB);
        }
    }
}