BackgroundWorker Thread used for Serial port data processing Throwing "This BackgroundWorker is currently busy and cannot run multiple tasks concurrently"

Question

Hello Guys, I am developing a application in C# which is getting data from Serial Port, Processing it and showing it to UI. The data is coming very fast between 5-50ms speed. Before I was not using any threads. and so application was relying on single App thread which was getting data from Serial Port, Processing data and showing it to UI. and It was loosing some data. Then I started implementing BackgroundWorker thread to remove some overhead on single thread and thinking of good performance. And Now I am getting "This BackgroundWorker is currently busy and cannot run multiple tasks concurrently" error. I think Thread is not able to cope up with the speed the data coming from Serial port. and So throwing error on executing "backgroundWorker1.RunWorkerAsync(data);". I need some suggestions what's the better approach to implement such kind of scenario?

Thanks in Advance -Chetan

Answer 1

The problem is that you're calling backgroundWorker1.RunWorkerAsync() before it's finished with its previous operation.

What you probably want to have is a single thread reading the serial port, buffering the data and notifying the main UI thread that data is available.

Answer 2

Try adding this in, to make sure the background worker is only running one job at a time.

if(!backgroundWorker1.IsBusy)
    backgroundWorker1.RunWorkerAysnc();

You also have the ability to cancel the current job, here is a code sample

    private void WhereBackworkerStarts()
    {
        backgroundWorker.WorkerSupportsCancellation = true;

        if (backgroundWorker.IsBusy)
            backgroundWorker.CancelAsync();
        else
            backgroundWorker.RunWorkerAsync();
    }

    // Events
    static void backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        for(int i = 0; i < int.MaxValue; i++)
        {
            if (backgroundWorker.CancellationPending)
            {
                e.Cancel = true;
                return;
            }

            // Do work here
        }
        e.Result = MyResult;
    }

    static void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        // Deal with results
    }

Answer 3

geofftnz is correct, and I'll expand a bit for you. You should only start the background worker once, and have it feed the data back to the GUI thread using ReportProgress. worker thread would look something like this.

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker worker = sender as BackGroundWorker;
    while(!e.CancellationPending)
    {
        ResultObject ro = new ResultObject();  // your own type here, obviously
        //Process and store some data in ro;
        worker.ReportProgress(0, ro);
        //Do not modify ro after reporting progress to avoid threading issues
    }
}

From the GUI, register to the ProgressChanged event, and only start the worker one time.