如何在 .net 中使用 MVVM 模式跟踪特定文件更改？

Question

我正在使用 Visual Studio 2022 开发一个 .NET WPF 项目，我向我的应用程序添加了托盘图标功能。 我在 mainwindow.xaml.cs 中管理托盘图标部分，但我还需要在我的 mainviewmodel class 中跟踪文件更改。 我如何将此事件传递给 mvvm 或者将数据传递给 mainviewmodel？ 任何帮助，将不胜感激。

public void CreateFileWatcher(string path)
        {
            watcher = new FileSystemWatcher();
            watcher.Path = path;
            watcher.NotifyFilter = NotifyFilters.LastWrite;
            watcher.Filter = nameof(AppStateModel);
            watcher.Changed += new FileSystemEventHandler(OnChanged);
            watcher.EnableRaisingEvents = true;
        }
    private void OnChanged(object source, FileSystemEventArgs e)
    {
        Thread.Sleep(1000);
        var appState = CheckAppState();
        AppState = appState;
        string workingDirectory = Environment.CurrentDirectory;


        string projectDirectory = Directory.GetParent(workingDirectory).Parent.FullName;
        var path = Path.Combine(projectDirectory, "Assets");

        switch (appState)
        {
            case 1:
                m_notifyIcon.Icon = new System.Drawing.Icon(Path.Combine(path, "48x48_active.ico"));
                break;
            case 2:
                m_notifyIcon.Icon = new System.Drawing.Icon(Path.Combine(path, "48x48_inactive.ico"));
                break;
            case 4:
                m_notifyIcon.Icon = new System.Drawing.Icon(Path.Combine(path, "48x48_running.ico"));
                break;
            default:
                break;
        }
    }
    private int CheckAppState()
    {
        try
        {
            var tempFile = Path.Combine(AppWizard.Default.FolderPath, nameof(AppStateModel));

            if (!File.Exists(tempFile))
                return -1;

            var _path = tempFile;
            using (var stream = new FileStream
                (_path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
            {
                var appStateModel = JsonConvert.DeserializeObject<AppStateModel>(File.ReadAllText(tempFile));
                if (appStateModel != null)
                {
                    if (appStateModel.CurrentState == AppStates.Ready)
                        return 1;

                    else if (appStateModel.CurrentState == AppStates.Dead || appStateModel.CurrentState == AppStates.Expired)
                        return 2;

                    else if (appStateModel.CurrentState == AppStates.Busy)
                        return 4;
                }
            }
        }
        catch (Exception ex)
        {
            FileLogger.Default.WriteExceptionLog(ex);
        }
        return -1;
    }

Answer 1

观察者服务可能如下所示：

public class FileWatcherService
    {
        FileSystemWatcher watcher;
        public FileWatcherService()
        {
            CreateFileWatcher();
        }
        public event EventHandler<FileSystemEventArgs> FileChanged;
        
        public void CreateFileWatcher()
        {
            watcher = new FileSystemWatcher(@"C:\Temp");

            watcher.NotifyFilter = NotifyFilters.Attributes
                                 | NotifyFilters.CreationTime
                                 | NotifyFilters.DirectoryName
                                 | NotifyFilters.FileName
                                 | NotifyFilters.LastAccess
                                 | NotifyFilters.LastWrite
                                 | NotifyFilters.Security
                                 | NotifyFilters.Size;

            watcher.Changed += MakeANote;
            watcher.Created += MakeANote;
            watcher.Deleted += MakeANote;
            watcher.Renamed += MakeANote;
            watcher.Filter = "*.*";
            watcher.IncludeSubdirectories = true;
            watcher.EnableRaisingEvents = true;
        }
        private void MakeANote(object sender, FileSystemEventArgs e)
        {
            FileChanged?.Invoke(this, e);
        }
    }

一种简单的方法是将“watcher”放在 View Model 中：

public class MainViewModel :Binding
{
    FileWatcherService _fileWatcherService = new FileWatcherService();
    public MainViewModel()
    {
        _fileWatcherService.FileChanged += OnFileChanged;
    }

    private void OnFileChanged(object sender, FileSystemEventArgs e)
    {
        LastAction = e.ChangeType.ToString();
        File = e.Name;
    }

    string _lastAction;
    public string LastAction
    {
        get { return _lastAction; }
        set { _lastAction = value;NotifyPropertyChanged(nameof(LastAction)); }
    }
    string _file;
    public string File
    {
        get { return _file; }
        set { _file = value; NotifyPropertyChanged(nameof(File)); }
    }



}

示例 XAML 代码如下：

<Grid>
        <Grid.DataContext>
            <local:MainViewModel/>
        </Grid.DataContext>
        <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding File}"/>
            <TextBlock Text=" has "/>
            <TextBlock Text="{Binding LastAction}"/>
        </StackPanel>

    </Grid>