private void button1_Click(object sender, EventArgs e)

        {

            backgroundWorker1.RunWorkerAsync();

        }

        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)

        {

            for (int i = 0; i < 10; i++)

            {

                Thread.Sleep(500);

                backgroundWorker1.ReportProgress(i);

            }

        }

        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)

        {

            Debug.WriteLine($"{e.ProgressPercentage}");

        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

        {

            Debug.WriteLine($"over!");

        }