How To Start And Stop A Continuously Running Background Worker Using A Button

Let's say I have a background worker like this:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
             while(true)
             {
                  //Kill zombies
             }
        }

How can I make this background worker s开发者_StackOverflow中文版tart and stop using a button on a WinForm?

Maybe you can use a manualresetevent like this, I didn't debug this but worth a shot. If it works you won't be having the thread spin its wheels while it's waiting

ManualResetEvent run = new ManualResetEvent(true);

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) 
{ 
     while(run.WaitOne()) 
     { 
         //Kill zombies 
     } 
} 

private void War() 
{ 
    run.Set();
} 

private void Peace() 
{ 
    run.Reset();
}

Use the CancelAsync method.

backgroundworker1.CancelAsync();

In your loop inside the worker thread.

if (backgroundWorker.CancellationPending) return;

This doesn't happen immediately.

This is how to do it (link to answer below)

By stop do you really mean stop or do you mean pause? If you mean stop, then this is a piece of cake. Create a button click event handler for the button you want to be responsible for starting the background worker and a button click event handler for the one responsible for stopping it. On your start button, make a call to the background worker method that fires the do_work event. Something like this:

private void startButton_Click(System.Object sender, 
    System.EventArgs e)
{
    // Start the asynchronous operation.
    backgroundWorker1.RunWorkerAsync();
}

On your stop button, make a call to the method that sets the background worker's CancellationPending to true, like this:

private void cancelAsyncButton_Click(System.Object sender, 
    System.EventArgs e)
{   
    // Cancel the asynchronous operation.
    this.backgroundWorker1.CancelAsync();
}

Now don't forget to check for the CancelationPending flag inside your background worker's doWork. Something like this:

   private void KillZombies(BackgroundWorker worker, DoWorkEventArgs e)
   {
        while (true)
        {
            if (worker.CancellationPending)
           {   
              e.Cancel = true;
           }
        }
   }

And your doWork method:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
             BackgroundWorker worker = sender as BackgroundWorker;
             KillZombies(worker, e);
        }

I hope this can steer you in the right direction. Some further readings:

http://msdn.microsoft.com/en-us/library/b2zk6580(v=VS.90).aspx

http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx

http://msdn.microsoft.com/en-us/library/waw3xexc.aspx

I haven't tested this, I have code somewhere that I'll have to see exactly what I did, but something like this is an adaptation of Fredrik's answer:

private bool _performKilling;
private object _lockObject = new object();

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
     while(true)
     {

         if (_performKilling)
         {
             //Kill zombies
         }
         else
         { //We pause until we are woken up so as not to consume cycles
             Monitor.Wait(_lockObject);
         }
     }
}

private void StartKilling()
{
    _performKilling = true;
    Monitor.Pulse(_lockObject);
}

private void StopAllThatKilling()
{
    _performKilling = false;
]

More complete example of this pattern here:

https://github.com/AaronLS/CellularAutomataAsNeuralNetwork/blob/fe9e6b950e5e28d2c99350cb8ff3157720555e14/CellLifeGame1/Modeling.cs