Threadpool

Creating threads can prove to be expensive, this is why there's a threadpool, class who's purpose is to keep a bunch of threads ready for your use to do threading stuff:

• execute tasks
• post work items
• process asynchronous IO
• etc

Threads created by the threadpool class are by default background threads, meaning your application won't wait for them if all foreground threads finish the app will close

using System;

using System.Threading;

namespace pc.threadpoolExample

{

    class Program

    {

        static void Main(string[] args)

        {

            //create background thread via threadpool

            ThreadPool.QueueUserWorkItem(o => {

                Thread.Sleep(500);//fires before main finishes

                Console.WriteLine("Hello from the thread pool 1");

            });

            //create background thread via threadpool

            ThreadPool.QueueUserWorkItem(o=> {

                Thread.Sleep(2000);// never fires, because main finishes

                Console.WriteLine("Hello from the thread pool 2");

            });

            var t = new Thread(() => {

                Thread.Sleep(1000);

                Console.WriteLine("hello from foregorund thread");

            });

       

            //start explicit thread

            t.Start();

            //join thread back to main

            t.Join();

            Console.WriteLine("Main finished");

        }

    }

}

generally you wont create threads explicitly or via the threadpool class, odds are you'll leverage

• the Task Parallel library (TPL) 
• the async/await keywords which abstract the TPL. 
• the Asynchronous Pattern Model
• the Event based Asynchronous Pattern   
• the Task based Asynchronous Pattern Model