它使所有调用线程等待，直到当前线程（加入的线程）终止或完成其任务。
using System;
using System.Threading;
public class MyThread
{
public void Thread1()
{
for (int i = 0;
i <
5;
i++)
{
Console.WriteLine(i);
Thread.Sleep(200);
}
}
}
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();
}
}【C#线程加入join】输出：
0
1
2
3
4
0
0
1
1
2
2
3
3
4
4
