Backgroundworker的RunWorkerCompleted事件甚至在完成工作之前就开始了

Question

我使用BackgroundWorker线程执行一个长任务（基本上读取一个大的xml文件）。工作人员第一次按照需要正常工作，但如果我上传第二个xml文件，使用相同的后台工作程序，它有时可以正常工作，但大多数情况下，即使在DoWork事件之前，BackgroundWorker的RunWorkerCompleted也会被触发。部分代码显示如下

    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是全局定义的变量。这里有什么问题我没有得到。请帮助

Answer 1

在调用DoWork之前，您应该添加RunWorkerAsync()事件处理程序（以及所有其他事件处理程序）。

否则，可能会发生RunWorkerAsync几乎什么也没做。

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();

在订阅RunWorkerAsync和DoWork事件后应该召集RunWokerCompleted。

Answer 3

你应该首先检查后台工作人员是否忙碌，使用这....

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

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

        }

Answer 4

正如在https://stackoverflow.com/a/16809596/8029935中所说的那样，你可以盲目地假设工人已完成工作并在DoWork方法因异常而死亡时产生结果。它由BackgroundWorker捕获并作为e.Error属性传递给RunWorkerCompleted事件处理程序。

所以，我建议您必须使用try / catch语句检查该属性。