通过显示表单订阅Observable不会绘制控件

问题描述

我在FileSystemWatcher周围有一个Observable包装器。

public readonly FileSystemWatcher Watcher;
public ObservableFileSystemWatcher(FileSystemWatcher watcher)
{
    if (watcher is null) throw new ArgumentNullException(nameof(watcher));

    Watcher = watcher;

    Changed = Observable
        .FromEventPattern<FileSystemEventHandler,FileSystemEventArgs>(h => Watcher.Changed += h,h => Watcher.Changed -= h)
        .Select(x => x.EventArgs);

    Renamed = Observable
        .FromEventPattern<RenamedEventHandler,RenamedEventArgs>(h => Watcher.Renamed += h,h => Watcher.Renamed -= h)
        .Select(x => x.EventArgs);

    Deleted = Observable
        .FromEventPattern<FileSystemEventHandler,FileSystemEventArgs>(h => Watcher.Deleted += h,h => Watcher.Deleted -= h)
        .Select(x => x.EventArgs);

    Errors = Observable
        .FromEventPattern<ErrorEventHandler,ErrorEventArgs>(h => Watcher.Error += h,h => Watcher.Error -= h)
        .Select(x => x.EventArgs);

    Created = Observable
        .FromEventPattern<FileSystemEventHandler,FileSystemEventArgs>(h => Watcher.Created += h,h => Watcher.Created -= h)
        .Select(x => x.EventArgs);
}

在这样的ApplicationContext（托盘程序）中观察到所说的Observable：

private void Watchers_Start()
{
    _filesystemwatchers?.Clear();
    foreach (var path in _pathstocheck)
    {
        try
        {
            ObservableFileSystemWatcher fsw = new ObservableFileSystemWatcher(c => { c.Path = path; c.IncludeSubdirectories = false; });
            fsw.Created
                .Where(_ => _.ChangeType is WatcherChangeTypes.Created)
                .Select(_ => _.FullPath)
                .Where(_ => !Path.GetFileName(_).StartsWith("~"))
                .Where(File.Exists)
                .Where(_ => ((DateTime.UtcNow - new DateTime(_lastFilesystem_Event)).TotalSeconds > _minDelayInSec))
                .distinctUntilChanged()
                .Subscribe(Filesystem_Event);

            fsw.Errors.Subscribe(x => LogMsg($"ObservableFileSystemWatcher().Error {x.GetException().Message}",true));

            _filesystemwatchers.Add(fsw);
            fsw.Start();
        }
        catch (Exception exc) when (LogMsg(exc)) { }
    }
}

在每个事件上调用的方法是：

private void Filesystem_Event(string flPath)
{
try
{
    if (_playSound)
        PlaySound();

    if (_openPopup)
        OpenPopup($"{DateTime.Now.ToString("dd/MM/yyyy HH:mm:ss")}{Environment.NewLine} blahblah",flPath);
}
catch (Exception ex) when (LogMsg(ex)) { }
}

依次调用以下内容以向用户显示表单（PopupForm只是常规表单）：

private void OpenPopup(string message,string filepath = "")
{
    if (message is null) message = string.Empty;

    LogMsg($"OpenPopup({message})");
    _popupWindow = new PopupForm();
    _popupWindow.Show();
}

好吧，如果我从ApplicationContext的任务栏图标上单击鼠标右键，然后选择显示测试通知，则它可以正常工作。这只是常规的C＃事件。

 _notifyIcon.ContextMenu = new ContextMenu(new MenuItem[]
{
    new MenuItem("Riavvia",new EventHandler(RestartEventHandler)),new MenuItem("Configura",new EventHandler(ShowConfig)),new MenuItem("Test Audio",new EventHandler(PlayTestSound)),new MenuItem("Test Popup",new EventHandler(OpenTestPopup)),new MenuItem("Test Email",new EventHandler(SendTestemail)),new MenuItem("Test Errore",new EventHandler(SendTestException)),new MenuItem("Esci",new EventHandler(Exit))
});

/// which in turn calls 
private void OpenTestPopup(object sender,EventArgs e)
{
    OpenPopup("TEST POPUP");
}

一切正常！

但是，如果我使用的是FileSystemWatcher调用OpenPopup方法（在文件系统事件上）的方法，则该表单将无法完全绘制。

我感觉到SynchronizationContext问题或死锁问题，或两者兼而有之。 在序列完成之前，Observable可能不会完全返回吗？ 如果我选择显示一个普通的MessageBox（使我感到困惑），则上述情况不会发生。

我已经尝试过：

• 将ObservableFileSystemWatcher强制使用其他调度程序
• 将ApplicationContext的SynchronizationContext传递给ObservableFileSystemWatcher
• 强制ObservableFileSystemWatcher在Scheduler.CurrentThread上运行

修改 我理解Panagiotis Kanavos想要说的是，在另一个线程上观察，然后在UI线程中 subscribe 。我的问题是，ApplicationContext不是UI，它只能启动表单（它是一个托盘图标）。

如果我以这种方式重构ObservableFileSystemWatcher，

public ObservableFileSystemWatcher(FileSystemWatcher watcher)
{
    if (watcher is null) throw new ArgumentNullException(nameof(watcher));

    Watcher = watcher;

    Changed = Observable
        .FromEventPattern<FileSystemEventHandler,h => Watcher.Changed -= h)
        .ObserveOn(NewThreadScheduler.Default)
        .Select(x => x.EventArgs);
    // blabla
}

这样观察它

.SubscribeOn(dispatcherScheduler.Current)

我（理应如此）得到一个InvalidOperationException “当前线程没有与之关联的dispatcher。” 因为ApplicationContext不是WinForm。

解决方法

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