Question

In a win form application, I have an array of threads which are started like this:

bool stop = false;
Thread[] threads = new Thread[10];

for (int i = 0; i < threads.Length; i++)
    threads[i] = new Thread(new ThreadStart(Job));

// How to make sure all threads have exited, when the boolean = false

void Job()
{
    while (!stop)
        // Do something
}

Now if user press STOP, the boolean value for stop will set to true, so threads exit the Job method one after another. How can I make sure all threads are exited?

NOTE: I need traditional threading for my case and TaskLibrary doesn’t fit my scenario.

Answer 1

Have you thought about using BackgroundWorkers instead? You said “traditional threads”..I’m not exactly sure what you mean so I don’t know if this is a valid proposal or not, but here it is anyways in case Join() doesn’t solve your problem

BackgroundWorker[] workers = new BackgroundWorker[10];
bool allThreadsDone = false;

// initialize BackgroundWorkers
for (int i = 0; i < 10; i++)
{
        workers[i] = new BackgroundWorker();
        workers[i].WorkerSupportsCancellation = true;
        workers[i].RunWorkerCompleted += 
            new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
        workers[i].DoWork += new DoWorkEventHandler(AlgorithmsUI_DoWork);
        workers[i].RunWorkerAsync();
}

// thread entry point..DoWork is fired when RunWorkerAsync is called
void AlgorithmsUI_DoWork(object sender, DoWorkEventArgs e)
{
      while (!stop)
            // do something        
}

// this event is fired when the BGW finishes execution
private void  worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    bool threadsStillRunning = false;
    foreach (BackgroundWorker worker in workers)
    {
        if (worker.IsBusy)
        {
            threadsStillRunning = true;
            break;
        }
    }
    if (!threadsStillRunning)
        allThreadsDone = true;
} 

protected override OnFormClosing(FormClosingEventArgs e)
{
         if (!allThreadsDone)
         {
              e.Cancel = true;
              MessageaBox.Show("Threads still running!");
         }
}

This should prevent your form from closing if any threads are still running.