Question

I am trying to make a stop button for this loop but it runs indefinite, nothing happens when i click button 2

bool dowhile = false;
private void button1_Click(object sender, EventArgs e)
{
    do
    {
        for (int i = listbox1.Items.Count - 1; i >= 0; i--)
        {
            string textstring = listbox1.Items[i].ToString();
            richTextBox1.AppendText("" + textstring + ": Done\n");
            Thread.Sleep(1000);
        }
    } while (!dowhile);
}
private void button2_Click(object sender, EventArgs e)
{
    this.dowhile = true;
}

where do i go wrong ?

sry for the “lvlchanger” typo, code is ok now, nothing missing

i’m also looking for a not-so-long fix on this :))

Answer 1

Thread.Sleep is almost always the incorrect approach; when you find yourself wanting to use something like it or Application.DoEvents in your code, it’s time to take a long step back and think about what you’re really doing and why it isn’t working. A new design should be in your future.

The real problem here is that you’re doing work on the UI thread, which blocks the user from interacting with your application. Your click on Button2 is getting recognized and processed after the loop has already finished processing, at which point it does absolutely nothing.

This is because threads can only complete one task at a time. And, in fact, Thread.Sleep(100) only makes this worse, because it forces the thread to spin and do nothing for 100 milliseconds. That’s 100 more milliseconds it will take for the loop to complete for absolutely no gain.

The correct solution to this (common) problem is to spin the loop off onto a separate thread, using something like the BackgroundWorker class. The MSDN entry has a very good example of its use, including your specific use case: allowing the user to cancel a long-running background task.