winform中怎么使用threadpool

winform中如何使用threadpool

C# code

       private void button2_Click(object sender, EventArgs e)        {            waitCallback = new WaitCallback(MyThreadWork);            ThreadPool.QueueUserWorkItem(waitCallback, "第一个线程");            ThreadPool.QueueUserWorkItem(waitCallback, "第二个线程");            ThreadPool.QueueUserWorkItem(waitCallback, "第三个线程");            ThreadPool.QueueUserWorkItem(waitCallback, "第四个线程");        }        public void MyThreadWork(object state)        {            int i=0;            while (i<20)            {                i++;                SetText(string.Format("线程现在开始启动…… {0}", (string)state));                Thread.Sleep((new Random(5)).Next()*1000);                SetText(string.Format("运行结束…… {0}", (string)state));            }        }        public delegate void mydeleg(string str);         public void SetText(string str)        {            if (textBox1.InvokeRequired)            {                textBox1.Invoke(new mydeleg(SetText),str);            }            else                textBox1.Text = str;        }