线程池

private void button1_Click(object sender, EventArgs e)
{
for (int i =3000; i < 3020; i++)
{
//再循环里向线程池添加为了多分几个线程
WaitCallback wca = new WaitCallback(ff);
ThreadPool.QueueUserWorkItem(wca, i);//放到应用池中参数一委托wca

}
}
private void ff(object obj)
{
int a = Convert.ToInt32(obj);
try
{
WebClient wc = new WebClient();
wc.DownloadFile(@"http://job.cnblogs.com/offer/" + a + "/", @"D:\html\" + a + ".html");
Invoke(new Action(delegate() //放到主线程中执行才可以显示
{
textBox1.AppendText ( "这是" + a + "个");
}));

}
catch { }
}