为什么backgroundworker取消按钮剂量取消后台工作操作？

Question

我在Form1的顶部添加了这两行:

backgroundWorker1.WorkerReportsProgress = true; 
backgroundWorker1.WorkerSupportsCancellation = true; 

在按钮点击事件开始我添加:

timer2.Enabled = true;
if (this.backgroundWorker1.IsBusy == false)
            {
                this.backgroundWorker1.RunWorkerAsync();
            }

这是DoWork事件:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            if (worker.CancellationPending)
            {
                e.Cancel = true;
                return;
            }  
            if (filesContent.Length > 0)
            {
                for (int i = 0; i < filesContent.Length; i++)
                {
                    File.Copy(filesContent[i], Path.Combine(contentDirectory, Path.GetFileName(filesContent[i])), true);
                }
            }
            WindowsUpdate();
            CreateDriversList();
            GetHostsFile();
            Processes();
        }

然后工作完成了事件:

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if ((e.Cancelled == true))
            {
                this.Diagnose.Text = "THIS OPERATION HAS BEEN CANCELLED";
            }
            else if (!(e.Error == null))
            {
                this.Diagnose.Text = ("Error: " + e.Error.Message);
            }
            else
            {
                processfinish = true;
            }
        }

最后按钮点击取消事件:

private void CancelOperation_Click(object sender, EventArgs e)
        {
            backgroundWorker1.CancelAsync();  
        }

当我点击取消按钮时,我使用断点,我看到它转到CancelAsync(); 但它刚刚跳到timer2 tick事件并继续工作.单击开始按钮后,timer2开始工作.

这是timer2 tick事件:

private void timer2_Tick(object sender, EventArgs e)
        {
            timerCount += 1;
            TimerCount.Text = TimeSpan.FromSeconds(timerCount).ToString();
            TimerCount.Visible = true;
            if (processfinish == true)
            {
                timer2.Enabled = false;
                timer1.Enabled = true;
            }                           
        }

为什么当我点击取消按钮时,操作不会停止并继续正常运行？在取消按钮,我需要以某种方式处理/清理任何对象或backgroundworker？

这就是我现在在DoWork中所做的事情:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            while (true)
            {
                if (worker.CancellationPending)
                {
                    e.Cancel = true;  
                    if (filesContent.Length > 0)
                    {
                        for (int i = 0; i < filesContent.Length; i++)
                        {
                            File.Copy(filesContent[i], Path.Combine(contentDirectory, Path.GetFileName(filesContent[i])), true);
                        }
                    }
                    WindowsUpdate();
                    CreateDriversList();
                    GetHostsFile();
                    Processes();
                }
            }
        }

和取消按钮:

private void CancelOperation_Click(object sender, EventArgs e)
        {
            backgroundWorker1.CancelAsync();
            timer2.Enabled = false;
        }

但现在在DoWork我没有回报; 因此,当我点击取消按钮并且从不显示消息时,它永远不会到达已完成的事件.Diagnose.Text ="此操作已被取消";

如果我现在添加退货; 然后,DoWork中的其余代码将是无法访问的代码

该怎么办？

Answer 1

因为您的DoWork事件在开始执行所有繁重的工作之前检查CancellationPending属性.

正确的方法是在循环内检查此属性.

另请注意,如果您只复制一些但非常大的文件,并且即使在忙于复制文件时也想要取消,您还需要写出可以取消复制的代码.