为什么幕后工作人员永远无法完成活动

在DoWork事件中，我做了：

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker bgw = (BackgroundWorker)sender;
            distance = 0; counter = 0;
            if (bgw.CancellationPending == true)
            {
            }
            else
            {
                while (counter < 200)
                {
                    counter += 1;
                    distance = (float)counter;
                    DateTime dt1, dt2;
                    dt1 = DateTime.Now;
                    CloudEnteringAlert.cloudalert(localbmp, distance);
                    dt2 = DateTime.Now;
                    TimeSpan ts = dt2 - dt1;
                    Logger.Write(ts.TotalMilliseconds.ToString());
                    if (counter == 199)
                    {
                        counter = 0;
                        CloudEnteringAlert.ClearList();
                        //break;
                    }
                    try
                    {
                        if (completed == true)
                        {
                            return;
                        }
                        else
                        {
                            this.Invoke(new Action(() =>
                            {
                                if (CloudEnteringAlert.cloudsfound == true)
                                {
                                    listBox1.Items.Add("Cloud detected at: " + CloudEnteringAlert.cloudsdistance.Text + " Kilometers from the coast");
                                    timesdetectedclouds += 1;
                                    label2.Visible = true;
                                    label2.Text = timesdetectedclouds.ToString();
                                }
                                else
                                {
                                    listBox1.Items.Add("Cloud not detected at: " + CloudEnteringAlert.cloudsdistance.Text + " Kilometers from the coast");
                                    timesnotdetectedclouds += 1;
                                    label4.Visible = true;
                                    label4.Text = timesnotdetectedclouds.ToString();
                                }
                            }));
                        }
                    }
                    catch (Exception err)
                    {
                        Logger.Write(err.ToString());
                    }
                }
            }
        }

在我完成的活动中：

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if ((e.Cancelled == true))
            {
            }
            else if (!(e.Error == null))
            {
            }
            else
            {
               string t = "Done!";
               completed = true;
            }

但它从未在完成的赛事中进入国际单项体育联合会。

我通常想做的是在DoWork事件中只向listBox1添加一次项。但它一次又一次地不停地做着。如果我要使用Break；此处：

if (counter == 199)
                    {
                        counter = 0;
                        CloudEnteringAlert.ClearList();
                        //break;
                    }

它将到达已完成的事件并停止。但我不想阻止backgorundworker，我只想用listBox1做一次，当它达到199时，不要再继续添加到listBox1，而是继续做其他事情。