等到我的BackgroundWorker完成，以打开新的BackgroundWorker

本文关键字：BackgroundWorker 我的完成 | 更新日期: 2023-09-27 18:15:36

在我的应用程序中，我在添加到我的列表框之前通过打开Wireshark进程检查我的文件。这是添加目录，点击事件，查看根文件夹和子文件夹中的所有文件:

private void btnAddDir_Click(object sender, EventArgs e)
{
    try
    {
        if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
        {
            ThreadStart threadStart = delegate
            {
                foreach (string file in SafeFileEnumerator.EnumerateFiles(folderBrowserDialog1.SelectedPath, "*.*", SearchOption.AllDirectories))
                {
                    Interlocked.Increment(ref numWorkers);
                    StartBackgroundFileChecker(file);
                }
            };
            Thread thread = new Thread(threadStart);
            thread.IsBackground = true;
            thread.Start();
        }
    }
    catch (Exception)
    { }
}
private void StartBackgroundFileChecker(string file)
{
    ListboxFile listboxFile = new ListboxFile();
    listboxFile.OnFileAddEvent += listboxFile_OnFileAddEvent;
    BackgroundWorker backgroundWorker = new BackgroundWorker();
    backgroundWorker.WorkerReportsProgress = true;
    backgroundWorker.DoWork +=
    (s3, e3) =>
    {
        //check my file
    };
    backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
    backgroundWorker.RunWorkerAsync();
}
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    if (Interlocked.Decrement(ref numWorkers) == 0)
    {
        //update my UI
    }
}

当我检查这个文件时，我打开Wireshark进程，所以如果我选择有许多文件的文件夹，许多Wireshark进程打开，这需要很多内存，我怎么能等到我的BackgroundWorker完成，然后才打开新的?

据我所知，您希望每次只启动一个后台worker。如果是，那么尝试这个(基于System.Threading.AutoResetEvent)

//introduce additional field
private AutoResetEvent _workerCompleted = new AutoResetEvent(false);
//modify StartBackgroundFileChecker
private void StartBackgroundFileChecker(string file)
{
    ListboxFile listboxFile = new ListboxFile();
    listboxFile.OnFileAddEvent += listboxFile_OnFileAddEvent;
    BackgroundWorker backgroundWorker = new BackgroundWorker();
    backgroundWorker.WorkerReportsProgress = true;
    backgroundWorker.DoWork +=
    (s3, e3) =>
    {
        //check my file
    };
    backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
    backgroundWorker.RunWorkerAsync();
   //new code - wait for completion
   _workerCompleted.WaitOne();
}
//add completion notification to backgroundWorker_RunWorkerCompleted
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    if (Interlocked.Decrement(ref numWorkers) == 0)
    {
        //update my UI
    }
    //new code - notify about completion
    _workerCompleted.Set();
}

在这个解决方案中，你的后台线程将一个接一个地启动新的BackgroundWorker——这可能不是最优的(你可以完全避免BackgroundWorker，只需通过threadStart delegate中的Dispatch来更新UI)

在我看来，最好控制并行线程的数量，并在多个线程中处理文件，但线程数量有限。

这是另一种解决方案(基于System.Threading.Tasks命名空间):

 private void btnAddDir_Click(object sender, EventArgs e)
 {
   var selectedPath = folderBrowserDialog1.SelectedPath;
   Task.Factory.StartNew(() =>
        {
           
            var files = Directory.EnumerateFiles(selectedPath, "*.*", SearchOption.AllDirectories);
            Parallel.ForEach(files,
                             new ParallelOptions
                             {
                                     MaxDegreeOfParallelism = 10 // limit number of parallel threads here 
                             },
                             file =>
                             {
                                 //process file here - launch your process
                             });
        }).ContinueWith(
            t => { /* when all files processed. Update your UI here */ }
            ,TaskScheduler.FromCurrentSynchronizationContext() // to ContinueWith (update UI) from UI thread
        );
}

你可以根据你的具体需要调整这个解决方案。

使用的类/方法(参考MSDN):

TaskScheduler。FromCurrentSynchronizationContext
平行。ForEach Method (IEnumerable, ParallelOptions, Action)

也许像这样，而不是foreach保留一个文件列表，完成后只取第一个元素并更新您的列表

private List<string> _files;
private void btnAddDir_Click(object sender, EventArgs e)
{
    try
    {
        if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
        {
            _files = new List<string>(SafeFileEnumerator.EnumerateFiles(folderBrowserDialog1.SelectedPath, "*.*", SearchOption.AllDirectories));
            Interlocked.Increment(ref numWorkers);
            var file = _files.FirstOrDefault();
            if(file != null)
                StartBackgroundFileChecker(file);
        }
    }
    catch (Exception)
    { }
}
private void StartBackgroundFileChecker(string file)
{
    ListboxFile listboxFile = new ListboxFile();
    listboxFile.OnFileAddEvent += listboxFile_OnFileAddEvent;
    BackgroundWorker backgroundWorker = new BackgroundWorker();
    backgroundWorker.WorkerReportsProgress = true;
    backgroundWorker.DoWork +=
    (s3, e3) =>
    {
        //check my file
    };
    backgroundWorker.RunWorkerCompleted += backgroundWorker_RunWorkerCompleted;
    backgroundWorker.RunWorkerAsync();
}
void backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    if (Interlocked.Decrement(ref numWorkers) == 0)
    {
        //update my UI
        _files = _files.Skip(1);
        var file = _files.FirstOrDefault();
        if(file != null)
            StartBackgroundFileChecker(file);
    }
}