Note: There is a limit of 25 threads in a thread pool. That means if you

start 50 threads then only 25 threads is active at a time. As soon as a

thread finishes another thread is active from thread pool.

Avoiding uses of ThreadPool class when following situation raise

1.       Requires a foreground thread.

2.       Requires a thread to have a particular priority.

3.       Have task that can block threads for long period of time. The threadpool has a maximum number of threads, so a large number of threadsfrom the thread pool being blocked might prevent task from starting.

4.       Need to have stable identity associated with thread.

5.       Need to place threads into a single threaded apartment.

Implementation of ThreadPool class

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
namespace ThreadStartDemo
{
    classThreadPoolClassDemo
    {
        staticvoid Main(string[] args)
        {
            //Call QueueUserWorkItem method of ThreadPool claas
            //to send Thread in ThreadPool and pass object of
            //WaitCallback deleaget.
            ThreadPool.QueueUserWorkItem(newWaitCallback(ThreadProc));
            Console.WriteLine("Main Thread Started.");
            Thread.Sleep(10000);
            Console.WriteLine("Main Thread Exists.");
        }
        ///<summary>
        /// This method is passed to WaitCallback delegate.
        /// This method is used to print numbers from 1 to 50.
        /// Main thread exists in two case either time fiven in main sleep
        /// method over of number is printed from 1 to 50.
        ///</summary>
        ///<param name="stateInfo"></param>
        staticvoid ThreadProc(object stateInfo)
        {
            Console.WriteLine("Welcome from thread pool. I will count from 1 to 50");
            for (int i = 1; i <= 50; i++)
            {
                Console.WriteLine(i);
                Thread.Sleep(500);
            }
        }
    }
}

Execute above program to see the output.