c# - Backgroundworker 的 RunWorkerCompleted 事件甚至在完成工作之前就被触发

Question

我正在使用 BackgroundWorker 线程来执行一个长任务（基本上是读取一个大的 xml 文件）。工作人员第一次按要求正常工作，但如果我上传第二个 xml 文件，使用相同的后台工作人员有时工作正常，但大多数情况下，后台工作人员的 RunWorkerCompleted 甚至在 DoWork 事件之前被触发。部分代码如下所示

    private void openFile_Click(object sender, RoutedEventArgs e)
    {
          // Code removed for brevity
  worker = new BackgroundWorker();
            worker.RunWorkerAsync();
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.WorkerReportsProgress = true;
            worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
       }

        void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        DataImport();
        //worker.Dispose();
        //worker.Disposed += new EventHandler(worker_Disposed);
        //worker.DoWork -= worker_DoWork;
        //worker.RunWorkerCompleted -= worker_RunWorkerCompleted;
        //worker = null;
        //GC.Collect(GC.GetGeneration(worker), GCCollectionMode.Forced);
    }

worker 是一个全局定义的变量。我不明白这里有什么问题。请帮助

Answer 1

您应该在调用之前DoWork添加-event 处理程序（以及所有其他事件处理程序）。RunWorkerAsync()

否则，可能会发生RunWorkerAsync实际上什么都不做的情况。

Answer 2

它应该是这样的：

worker = new BackgroundWorker();
worker.WorkerReportsProgress = true;

worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.ProgressChanged += 
    new ProgressChangedEventHandler(worker_ProgressChanged);
worker.RunWorkerCompleted += 
    new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);

worker.RunWorkerAsync();

RunWorkerAsync应该在订阅DoWorkandRunWokerCompleted事件后调用。

Answer 3

你应该首先检查后台工作人员是否忙，使用这个....

        backgroundWorker1.DoWork += backgroundWorker1_DoWork;
        backgroundWorker1.RunWorkerCompleted += backgroundWorker1_RunWorkerCompleted;

        if (backgroundWorker1.IsBusy)
        {
            backgroundWorker1.CancelAsync();
        }
        else
        {
            backgroundWorker1.RunWorkerAsync();

        }

Answer 4

正如https://stackoverflow.com/a/16809596/8029935中所说，当 DoWork 方法因异常而死时，您可以盲目地假设工作人员已经完成了工作并产生了结果。它被 BackgroundWorker 捕获并作为 e.Error 属性传递给 RunWorkerCompleted 事件处理程序。

因此，我建议您必须使用 try/catch 语句检查该属性。