[C#]如何使用ThreadPool

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace ThreadPoolDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            const int FibonacciCalculations = 10;
            ManualResetEvent[] doneEvents = new ManualResetEvent[FibonacciCalculations];
            Fibonacci[] fibArray = new Fibonacci[FibonacciCalculations];
            Random r = new Random();
            Console.WriteLine("launching {0} tasks...", FibonacciCalculations);
            for (int i = 0; i < FibonacciCalculations; i++)
            {
                doneEvents[i] = new ManualResetEvent(false);
                Fibonacci f = new Fibonacci(r.Next(20, 40), doneEvents[i]);
                fibArray[i] = f;
                ThreadPool.QueueUserWorkItem(f.ThreadPoolCallback, i);
            }
            //wait for all threads in pool to calculate
            WaitHandle.WaitAll(doneEvents);
            for (int i = 0; i < FibonacciCalculations; i++)
            {
                Fibonacci f = fibArray[i];
                Console.WriteLine("Fibonacci({0})={1}", f.N, f.FibofN);
            }
            Console.Read();
        }
    }
    public class Fibonacci
    {
        private int _n;
        private int _fibofN;
        private ManualResetEvent _doneEvent;
        public int N { get { return _n; } }
        public int FibofN { get { return _fibofN; } }
        public Fibonacci(int n, ManualResetEvent doneEvent)
        {
            _n = n;
            _doneEvent = doneEvent;
        }
        public void ThreadPoolCallback(object threadContext)
        {
            int threadIndex = (int)threadContext;
            Console.WriteLine("thread {0} started....", threadIndex);
            _fibofN = Calculate(_n);
            Console.WriteLine("thread {0} result calculated...", threadIndex);
            _doneEvent.Set();
        }
        public int Calculate(int n)
        {
            if (n <= 1)
            {
                return n;
            }
            return Calculate(n - 1) + Calculate(n - 2);
        }
    }
}