代码运行时，进度条（选取框）消失

Question

I have a simple form with a button and a progress bar. User clicks the button to begin processing and the progress bar animates while the code runs. In this case, it's just a for loop. But the problem is that the progress bar only appears for a fraction of a second then disappears.

private void button1_Click(object sender, EventArgs e)
{
    progressBar1.Style = ProgressBarStyle.Marquee;
    progressBar1.MarqueeAnimationSpeed = 100;

    for (int i = 0; i < 3; i++) { Thread.Sleep(1000); } // sleep 3 times for 1 second

}

I assume this happens because the frame is redrawn after the code continues? So I tried running the for loop on another thread but it didn't seem to matter.

How can I get the bar to animate while the loop runs?

Thanks

Answer 1

You can simply workaround this by including a call to Application.DoEvents() on each iteration of your loop.

But this is not the best way to achieve this.

The recommended way is processing your loop inside another thread, like a BackgroundWorker, keeping your progressbar animating on the mainthread.

You can get some explanation here: Keeping your UI Responsive and the Dangers of Application.DoEvents