如何启动已停止的线程

Question

I create a new thread and start it from a main thread.

m_MyThread = new Thread(HandleMyThread);
m_MyThread.IsBackground = true;
m_MyThread.Start();

private void HandleMyThread()
{
    while (true)
    {
        Thread.Sleep(5000);
        return;
    }
}

After 5 seconds, this thread will finish and its ThreadState is Stopped. I want to start it again when user clicks on button but I get a ThreadStateException (Thread is running or terminated; it cannot restart) :

private void button1_Click(object sender, EventArgs e)
{
    m_MyThread.Start(); // ->raise exception
}

Please help me how to restart a stopped thread. Thanks.

Answer 1

I know this question is a bit old, but I thought I would post a response in case others come here.

For this example code, if it were changed to look like this:

Thread m_MyThread;
private void HandleMyThread()
{
    while (true)
    {
        Thread.Sleep(5000);
        return;
    }
}

private void button1_Click(object sender, EventArgs e)
{
    if (!m_MyThread.IsAlive)
    {
        m_MyThread = new Thread(HandleMyThread);
        m_MyThread.IsBackground = true;
        m_MyThread.Start();
    }
}

This would create a new instance of the thread and start it. The ThreadStateException error is because, simply, you can't re-start a thread that's in a stopped state. m_MyThread.Start() is only valid for threads in the Unstarted state. What needs done in cases like this is to create a new thread instance and invoke Start() on the new instance.

Answer 2

Use a ManualResetEvent , and instead of Thread.Sleep , wait for the event with a timeout.

Then, any other thread can activate the event, and immediately resume the sleeping thread.

Once a thread is exited, it can no longer run. So don't let it exit. Instead, put it back to sleep waiting for an event.

Answer 3

If you want to reuse the thread without new a thread every time, you can consider the implementation of thread pool.

Answer 4

Just make a new thread like you did when you initially created the thread. You might also want to pull that out into a method to avoid repeating yourself.

Answer 5

To restart a thread, try this:

private void button1_Click(object sender, EventArgs e)
{
    // Just create a new constructor for the stopped Thread
    m_MyThread = null;
    m_MyThread = new Thread(HandleMyThread);
    m_MyThread.IsBackground = true;
    // Then restart the stopped Thread
    m_MyThread.Start();
}

This works if the thread was previously stopped.