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我在我的应用程序中使用 BackgroundWorker。当 Backgroundworker 仍然很忙时，我可以显示进度条的变化。但是，当我使用 AutoResetEvent 等到 Backgroundworker 完成时，我没有看到进度条发生变化。有没有另一种方法，我可以等待 BackgroundWorker 完成并显示进度条更改？我对 C# 框架和编程很陌生。

private AutoResetEvent _resetEvent = new AutoResetEvent(false);

private void InitializeBackgroundWorker()
        {
            parserBackgroundWorker.DoWork +=
                new DoWorkEventHandler(parserBackgroundWorker_DoWork);
            parserBackgroundWorker.RunWorkerCompleted +=
                new RunWorkerCompletedEventHandler(
            parserBackgroundWorker_RunWorkerCompleted);
            parserBackgroundWorker.ProgressChanged +=
                new ProgressChangedEventHandler(
            parserBackgroundWorker_ProgressChanged);
            parserBackgroundWorker.WorkerReportsProgress = true;
            parserBackgroundWorker.WorkerSupportsCancellation = true;
        }

 private void parserBackgroundWorker_DoWork(object sender,
            DoWorkEventArgs e)
        {
            // Get the BackgroundWorker that raised this event.
            BackgroundWorker worker = sender as BackgroundWorker;

            parser.Parse((SegmentFile)e.Argument);
            _resetEvent.Set();
        }

        // This event handler deals with the results of the 
        // background operation. 
        private void parserBackgroundWorker_RunWorkerCompleted(
            object sender, RunWorkerCompletedEventArgs e)
        {
            // First, handle the case where an exception was thrown. 
            if (e.Error != null)
            {
                MessageBox.Show(e.Error.Message);
            }
            else if (e.Cancelled)
            {
                // Next, handle the case where the user canceled  
                // the operation. 
                // Note that due to a race condition in  
                // the DoWork event handler, the Cancelled 
                // flag may not have been set, even though 
                // CancelAsync was called.
                //resultLabel.Text = "Canceled";
            }
            else
            {
                // Finally, handle the case where the operation  
                // succeeded.
                //resultLabel.Text = e.Result.ToString();
            }           
        }

        // This event handler updates the progress bar. 
        private void parserBackgroundWorker_ProgressChanged(object sender,
            ProgressChangedEventArgs e)
        {
            ProgressBar1.Value = e.ProgressPercentage;
        }

parserBackgroundWorker.RunWorkerAsync(selectedSegFile);
// when I comment this code I do see the progress bar change as the thread is doing the work.
_resetEvent.WaitOne();
4

2 回答 2

1

假设您有以下代码：

parserBackgroundWorker.RunWorkerAsync(selectedSegFile);
_resetEvent.WaitOne();
MessageBox.Show("Work Done");

然后您可以将代码_resetEvent.WaitOne();放在方法之后并将此方法附加到RunWorkerCompleted事件并删除_resetEvent.WaitOne();

private void MyRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    MessageBox.Show("Work Done");
}

private void InitializeBackgroundWorker()
{
    //old init code
    // you can attach as many methods to RunWorkerCompleted as you want
    parserBackgroundWorker.RunWorkerCompleted += parserBackgroundWorker_RunWorkerCompleted;
    parserBackgroundWorker.RunWorkerCompleted += myRunWorkerCompleted;
}

您也可以将 adelegate作为参数BackgroundWorker并调用它parserBackgroundWorker_RunWorkerCompleted

class ParserWorkerParameters
{
    public String SegFile { get; set; }
    public Action CallBack { get; set; }

    public ParserWorkerParameters(string segFile, Action callBack)
    {
       SegFile = segFile;
       CallBack = callBack;
    }
}

parserBackgroundWorker.RunWorkerAsync(new ParserWorkerParameters("someString", () =>  MessageBox.Show("worker complete")));

private void parserBackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    ParserWorkerParameters param = e.Argument as ParserWorkerParameters;
    parser.Parse((SegmentFile)param.SegFile);
    e.Result = param;
}

private void parserBackgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    //old code
    ParserWorkerParameters param = e.Result as ParserWorkerParameters;
    if (param.CallBack != null)
    {
        param.CallBack();
    }
}
于 2014-07-18T21:56:58.643 回答
1

正如上面评论中已经讨论的那样，问题是您在调用该WaitOne方法时阻塞了 UI 线程。您BackgroundWorker实际上是在更新Value进度条的属性（并通过这样做使其无效），但是应该执行控件的实际绘制的线程被阻止等待事件。

根据您的评论，您似乎关心的是如何使用不同的参数启动工作程序，并RunWorkerCompleted根据这些参数以不同的方式处理事件。

一种方法可能是为该事件附加不同的处理程序，每当您从程序中的某个点启动工作程序时：

// attach the handler
parserBackgroundWorker.RunWorkerCompleted += FirstCaseHandler;

// run it
parserBackgroundWorker.RunWorkerAsync(selectedSegFile);

在这种情况下，每个处理程序应该做的第一件事就是分离自身：

void FirstCaseHandler(object sender, RunWorkerCompletedEventArgs e)
{
    // detach this specific handler
    parserBackgroundWorker.RunWorkerCompleted -= FirstCaseHandler;

    // do stuff
    ...
}

或者，您可以附加单个处理程序并使用它来根据工作人员结果处理不同的情况。

在这种情况下，您可以设置 的Result属性以在您的方法完成DoWorkEventArgs时将结果对象传递给处理程序：DoWork

void parserBackgroundWorker_DoWork(object sender,
        DoWorkEventArgs e)
{
     // do stuff
     var parserResult = parser.Parse((SegmentFile)e.Argument);

     // set the Result property with a custom object which 
     // will allow you to know which case you need to handle

     // this can be simply: e.Result = e.Argument;

     // or, you can create an instance of your own class, something like:
     e.Result = new WorkerResult(e.Argument, parserResult);
}

在这种情况下，您将检查处理程序e.Result内部的值RunWorkerCompleted：

void parserBackgroundWorker_RunWorkerCompleted(
       object sender, RunWorkerCompletedEventArgs e)
{
    var resultInfo = e.Result as WorkerResult; // or whatever

    // do the right thing based on its value
}

您甚至可以将回调委托作为参数传递并从RunWorkerCompleted处理程序调用此方法，因此您确实有很多选择。

于 2014-07-18T22:01:26.260 回答