总结：

thread能启动非常多的线程同时工作，但threadpool和Task同时并行的线程数有限，约20个左右，但Threadpool设置最大并行数后则不会超过此数。

另：thread和threadpool的子线程中如果有未处理的异常，则主程序则会出现“*** 已停止工作”这样的错误（程序自动退出），而Task的子线程中出现未处理的异常时不影响主程序，即主程序不会退出。

 

 public partial class Form1 : Form

    {

        int count = 0;

        int 总次数 = 0;

        Random r = new Random();

        public Form1()

        {

            InitializeComponent();

        }

        private void button1_Click(object sender, EventArgs e)

        {

            //有300多个线程并行

            this.count = 0;

            this.总次数 = 0;

            for (int m = 0; m < 400; m++)

            {

                System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(this.run));

                t.Start();

            }

        }

        private void button2_Click(object sender, EventArgs e)

        {

            //有10到40个线程并行

            this.count = 0;

            this.总次数 = 0;

            int a,b; //得到32767和1000

             System.Threading.ThreadPool.GetMaxThreads(out a,out b);

            for (int m = 0; m < 400; m++)

            {

                System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback( this.run),0);

            }

        }

        private void button5_Click(object sender, EventArgs e)

        {

            //有10到40个线程并行

            this.count = 0;

            this.总次数 = 0;

            int a, b; //得到32767和1000

            System.Threading.ThreadPool.GetMaxThreads(out a, out b);

            //设置为最大10后，并行数稳定在10个，设置最大100后，最多并行还是10到40个，这应该和机器有关

            System.Threading.ThreadPool.SetMaxThreads(10, 100);  

            for (int m = 0; m < 400; m++)

            {

                System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback(this.run), 0);

            }

        }

        private void button3_Click(object sender, EventArgs e)

        {

            //有10到40多个线程并行，运行效率基本同于QueueUserWorkItem

            this.count = 0;

            this.总次数 = 0;

           

            for (int m = 0; m < 400; m++)

            {

                System.Threading.Tasks.Task.Factory.StartNew(this.run);

            }

        }

        private void run()

        {

            Interlocked.Increment(ref this.总次数);

            Interlocked.Increment(ref this.count);

            System.Threading.Thread.Sleep(r.Next(10) * 1000);

            System.Threading.Interlocked.Decrement(ref this.count);

            this.异常();

        }

        private void run(object ob)

        {

            Interlocked.Increment(ref this.总次数);

            Interlocked.Increment(ref this.count);

         

            System.Threading.Thread.Sleep(r.Next(10) * 1000);

            System.Threading.Interlocked.Decrement(ref this.count);

            this.异常();

        }

        private void 异常()

        {

            throw new Exception("ddd");

            //try

            //{

            //    throw new Exception("ddd");

            //}

            //catch (Exception ex)

            //{

            //}

        }

        private void button4_Click(object sender, EventArgs e)

        {

            this.textBox1.Text = this.count.ToString() + " / " + this.总次数;

        }

      

    }