join()方法使所有的调用线程等待直到当前线程(已连接线程)终止或完成其任务。

参考以下示例 -

using system;
using system.threading;
public class mythread
{
    public void thread1()
    {
        for (int i = 0; i < 5; i++)
        {
            console.writeline("thread1 : "+i);
            thread.sleep(500);
        }
    }
}
public class threadexample
{
    public static void main()
    {
        mythread mt = new mythread();
        thread t1 = new thread(new threadstart(mt.thread1));
        thread t2 = new thread(new threadstart(mt.thread1));
        thread t3 = new thread(new threadstart(mt.thread1));
        t1.start();
        t1.join();
        t2.start();
        t3.start();
    }
}

执行上面示例代码，得到以下结果 -

thread1 : 0
thread1 : 1
thread1 : 2
thread1 : 3
thread1 : 4
thread1 : 0
thread1 : 0
thread1 : 1
thread1 : 1
thread1 : 2
thread1 : 2
thread1 : 3
thread1 : 3
thread1 : 4
thread1 : 4