using System;

using System.Collections.Generic;

using System.Threading;

public class Program

{

    public static void Main()

    {

        List<Thread> threads = new List<Thread>();

​

        for (int i = 0; i < 1000; i++)

        {

            int iCopy = i;

​

            var t = new Thread(() =>

                {

                    Thread.Sleep(1000);

                    Console.WriteLine($"Thread {iCopy}");

                })

                {IsBackground = true};

            threads.Add(t);

​

            t.Start();

        }

​

        Console.WriteLine("Done");

        Thread.Sleep(3000);

    }

}