C# This BackgroundWorker is currently busy and cannot run multiple tasks concurrently

Question

I get this error if I click a button that starts the backgroundworker twice.

"This BackgroundWorker is currently busy and cannot run multiple tasks concurrently"

How can I avoid this?

Thanks

Answer 1

Simple: Don't start the BackgroundWorker twice.

You can check if it is already running by using the IsBusy property, so just change this code:

worker.RunWorkerAsync();

to this:

if( !worker.IsBusy )
    worker.RunWorkerAsync();
else
    MessageBox.Show("Can't run the worker twice!");

Answer 2

Create a new BackgroundWorker object for each operation that you want to perform. E.g., rather than:

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
for (int i; i < max; i++) {
   worker.RunWorkerAsync(i);
}

Try this:

for (int i; i < max; i++) {
   BackgroundWorker worker = new BackgroundWorker();
   worker.DoWork += new DoWorkEventHandler(worker_DoWork);
   worker.RunWorkerAsync(i);
}

Answer 3

Hi all, somebody know can i kill this BackgroundWorker? i tried backgroundWorker1.CancelAsync() but it doesn't work.

Igor

Answer 4

I would look into queue'ing the tasks that need to be done. You get the following advantages;

• You do not have to handle the problems of background tasks not being able to start due to something else already running
• You do not have to worry about using up too many threads, by creating a new background worked for each task.
• Lastly the queue could allow you to ensure that the background tasks run in the same order as they where created/requested.

Here is an example implementation: http://thevalerios.net/matt/2008/05/a-queued-backgroundworker. I am not sure if the implementation in threadsafe, and I will update my answer once I figure out of my current locking problem in a implementation I am working with.