How to pause and resume a BackgroundWorker?

Question

This is how I did it in my code: In the backgroundWorker DoWork event I did:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            _busy.WaitOne();
                this.Invoke(new MethodInvoker(delegate { label2.Text = "Website To Crawl: "; }));
                this.Invoke(new MethodInvoker(delegate { label4.Text = mainUrl; }));
                webCrawler(mainUrl, levelsToCrawl, e);


        }

Then in the pause button click event I did:

private void button4_Click(object sender, EventArgs e)
        {
            _busy.Reset();
        }

In the resume button click event I did:

private void button5_Click(object sender, EventArgs e)
        {
            _busy.Set();
        }

But it's not working when I click to start the process:

private void button1_Click(object sender, EventArgs e)
        {
            backgroundWorker1.RunWorkerAsync();
            button1.Enabled = false;
            this.Text = "Processing...";
            label6.Text = "Processing...";
            label6.Visible = true;
            button2.Enabled = false;
            checkBox1.Enabled = false;
            checkBox2.Enabled = false;
            numericUpDown1.Enabled = false;
            button3.Enabled = true;
        }

Nothing happen only when I click the resume button the process start then when I click the pause button nothing happen.

I want that when I click the start process button it will start the backgroundWorker regular then when clicking the pause button it will pause and the resume button it will resume.

What did I do wrong ? Can someone fix my code ?

Answer 1

In your BackgroundWorker thread code, you need to find places that are safe to "pause" execution. The ManualResetEvent is the right way to code. This other post might help: Is there a way to indefinitely pause a thread?

Basically, in a few choice points in your worker thread code where you want to allow it to pause, try inserting:

_busy.WaitOne(Timeout.Infinite);

And when you want to pause (from your main thread) you use:

_busy.Reset();

And to resume:

_busy.Set();