using System;

using System.Collections;

using System.Collections.Generic;

using System.Diagnostics;

using System.Runtime;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Stopwatch stopWatch = new Stopwatch();

        List<Person> listLess, listMore, listCommonLess, listCommonMore;

        long less, more;

        listLess = new();

        listMore = new();

        listCommonLess = new();

        listCommonMore = new();

​

        for(int i=100; 1<1000; i+=10){

            listLess.Clear();

            listMore.Clear();

            listCommonLess.Clear();

            listCommonMore.Clear();

            for(int j=1; j<=i; j++){

                Person person = new Person();

                listLess.Add(person);

                listMore.Add(person);

​

            }

            for(int j=1; j<=i*i; j++){

                listMore.Add(new Person());

            }

            listLess = listLess.Distinct().ToList();

            listMore = listMore.Distinct().ToList();

            stopWatch.Restart();

            var common1 = from first in listLess

                join second in listMore

                //on first.LastName equals second.LastName

                on first equals second

                /*new { LastName = first.LastName, Age = first.Age } equals 

                new { LastName = second.LastName, Age = second.Age }*/

                select first;

            listCommonLess = common1.ToList();

            stopWatch.Stop();

            less = stopWatch.ElapsedMilliseconds;

            stopWatch.Restart();

            var common2 = from first in listMore

                join second in listLess

                on first equals second

                /*new { LastName = first.LastName, Age = first.Age } equals 

                new { LastName = second.LastName, Age = second.Age }*/

                //on first.FirstName equals second.FirstName

                select first;

            listCommonLess = common2.ToList();

            stopWatch.Stop();

            more = stopWatch.ElapsedMilliseconds;

            int commonCount = 0;

            commonCount = common1.Count() == common2.Count() ? common1.Count() : 0;

            Console.WriteLine("Less=" + listLess.Count.ToString() + " : " + less + " | More="+listMore.Count.ToString() + " : " + more + " :: Match:" + commonCount);

        }

    }

}

​

public class Person {

    public string FirstName { get; set; } = DateTime.Now.Second.ToString();

    public string LastName { get; set; } = DateTime.Now.Millisecond.ToString();

    public int Age { get; set; } = new Random(DateTime.Now.Millisecond).Next(10, 51);

    public override bool Equals(object obj){

        Person person = obj as Person; // Point2? if Point2 is a struct

        return person != null && this.Equals(person);

    }

    public bool Equals(Person person){

        return person.FirstName == this.FirstName && person.LastName == this.LastName && person.Age == this.Age;

    }

}