How to wait for background worker to finish processing?

Question

I have 3 background workers each processing a channel of a 24-bit Bitmap image (Y, Cb, Cr). The processing for each 8-bit image takes several seconds and they might not com

Answer 1

Consider using AutoResetEvents:

private void button1_Click(object sender, EventArgs e)
    {
        var e1 = new System.Threading.AutoResetEvent(false);
        var e2 = new System.Threading.AutoResetEvent(false);
        var e3 = new System.Threading.AutoResetEvent(false);

        backgroundWorker1.RunWorkerAsync(e1);
        backgroundWorker2.RunWorkerAsync(e2);
        backgroundWorker3.RunWorkerAsync(e3);


        // Keep the UI Responsive
        ThreadPool.QueueUserWorkItem(x =>
        {
            // Wait for the background workers
            e1.WaitOne();
            e2.WaitOne();
            e3.WaitOne();
            MethodThatNotifiesIamFinished();
        });

        //Merge Code
    }


    void BackgroundWorkerMethod(object obj)
    {
        var evt = obj as AutoResetEvent;
        //Do calculations
        etv.Set();
    }

This way you do not waste cpu time in some loops & using a seperate thread for waiting keeps the UI Responsive.