FileSystemWatcher 仅在第一次更改后引发

Question

我正在使用

FileSystemWatcher

。

一切正常。当我保存文件时，会正确引发 Changed 事件。 但如果我第二次保存文件，则不再引发 Changed 事件。

我是否需要添加额外的代码，以便每次保存文件时都会引发？

这是我的代码的一部分，如果这有任何帮助的话：

我做了一个课程

MachineWatcher

，因为在我的项目中，我需要创建不同观察者类型的列表（但我认为这不会改变问题）：

public class MachineWatcher
{
    private Machine machine { get; set; }
    public Machine Machine { get { return this.machine; } set { this.machine = value; } }
    private string typeWatcher { get; set; } = "";
    public string TypeWatcher { get { return this.typeWatcher; } set { this.typeWatcher = value; } }
    FileSystemWatcher watcher { get; set; }
    public FileSystemWatcher Watcher { get { return this.watcher; } set { this.watcher = value; } }
    public MachineWatcher()
    {

    }
    public MachineWatcher(string type,string directoryStock,string fileFilter)
    {
        this.typeWatcher = type;
        this.watcher = new FileSystemWatcher();
        this.watcher.Path = Path.GetDirectoryName(directoryStock);
        this.watcher.Filter = fileFilter;
        this.watcher.NotifyFilter = NotifyFilters.Size | NotifyFilters.LastWrite | NotifyFilters.CreationTime;
        this.watcher.Changed += new FileSystemEventHandler(OnFeedBackNesterCreated);
        this.watcher.Created += new FileSystemEventHandler(OnFeedBackNesterCreated);
        
        this.watcher.EnableRaisingEvents = true;
    }
    private void OnFeedBackNesterCreated(object source, FileSystemEventArgs e)
    {
        string filePath = e.FullPath;
        LaunchingOrder newLo = this.readXmlFile(filePath);
        if(newLo!=null)
        {
            newLo.Fichier = filePath;
            newLo.AddOrUpdate();
        }
    }
        
}

Answer 1

我的建议是尝试将

this.watcher.Renamed

添加到处理的事件中，然后在应用 Renamed 表达式时注意

not

过滤掉

this.watcher.NotifyFilter

事件。这至少可以弥补 Excel 执行从菜单调用的

Save

操作的方式。根据下面所示的测试方法，

Changed

事件永远不会被触发。当我制作一个模拟

MachineWatcher

并连接 all 包括

Renamed

在内的事件时，第一个事件发生在打开文件时创建名为 ~$ExcelTestFile.xlsx 的临时文件时。然后，每次发生

Save

操作时，都会发生以下序列：

1. Created

   临时文件事件（例如，在此过程中，它被任意命名为 ECA83C30）。
2. 此 tmp 文件会触发两个

   Changed

   事件（大概是因为主文件的修改版本被复制到其中）。

3. Renamed

   D03DF176.tmp 事件（大概来自 ECA83C30）

4. Renamed

   real 目标的事件，名为 ExcelTestFile.xlxs 的文件（可能是来自 D03DF176.tmp 的复制操作）

5. Delete

   D03DF176.tmp
的活动

但是没有

Change

目标Excel文件的事件即使它最终得到一个新的

LastWriteTime

。这让我很震惊，但看看你是否可以重现！

---

模拟最小的

MachineWatcher

public class MachineWatcher
{
    public MachineWatcher(string type, string directoryStock, string fileFilter)
    {
        watcher = new FileSystemWatcher(directoryStock, fileFilter);
        watcher.Created += onModified;
        watcher.Changed += onModified;
        watcher.Renamed += onModified;
        watcher.Deleted += onModified; 
        // watcher.NotifyFilter = NotifyFilters.Size | NotifyFilters.LastWrite | NotifyFilters.CreationTime;
        watcher.EnableRaisingEvents = true;
    }
    FileSystemWatcher watcher { get; }

    private void onModified(object sender, FileSystemEventArgs e)
    {
        switch (e.ChangeType)
        {
            case WatcherChangeTypes.Created:
                OnFeedBackNesterCreated(sender, e);
                Console.WriteLine($" LastWriteTime: {new FileInfo(e.FullPath).LastWriteTime}");
                break;
            case WatcherChangeTypes.Deleted:
                Console.WriteLine($"Deleted: {e.Name}");
                break;
            case WatcherChangeTypes.Changed:
                var ext = Path.GetExtension(e.FullPath);
                switch (ext)
                {
                    case ".xlsx":
                        Console.Write($"Changed: {e.Name}");
                        break;
                    case ".txt":
                        try
                        {
                            Console.Write($"Changed: {e.Name} {File.ReadAllLines(e.FullPath).Last()}");
                        }
                        catch
                        {
                            Console.Write($"Changed: {e.Name} (in transition)");
                        }
                        break;
                    case "":
                        Console.Write($"Changed: {e.Name} (no extension)");
                        break;
                    default:
                        Console.Write($"The '{ext}' extension is not supported");
                        break;
                }
                Console.WriteLine($" LastWriteTime: {new FileInfo(e.FullPath).LastWriteTime}");
                break;
            case WatcherChangeTypes.Renamed:
                Console.Write($"Renamed: {e.Name}");
                Console.WriteLine($" LastWriteTime: {new FileInfo(e.FullPath).LastWriteTime}");
                break;
            default:
                break;
        }
    }

    private void OnFeedBackNesterCreated(object source, FileSystemEventArgs e)
    {
        Console.Write($"Created: {e.Name}");
    }
}

---

使用控制台练习

MachineWatcher

static void Main(string[] args)
{
    const int SPACING = 500;
    string appData = Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
        "custom_file_system_watcher");

    // Ensure that the root directory exists
    Directory.CreateDirectory(appData);

    // Make an instance of MachineWatcher
    var mw = new MachineWatcher(
        null, // In minimal reproducible sample this is unused
        appData, 
        "*.*");

    // Force Delete (if exists)
    var testFile = Path.Combine(appData, "testFile.txt");
    File.Delete(testFile);
    Thread.Sleep(SPACING);

    // Force Create + Change
    File.WriteAllText(
            testFile, 
            $"{DateTime.Now}{Environment.NewLine}");
    Thread.Sleep(SPACING);

    // Force N Changes
    var N = 5;
    for (int i = 1; i <= N; i++)
    {
        // Using Append because File.WriteAllText is two events not one.
        File.AppendAllText(testFile, $"Change #{i}{Environment.NewLine}");
        Thread.Sleep(SPACING);
    }

    // Force Rename
    var testFileRenamed = Path.Combine(appData, "testFile.Renamed.txt");
    File.Copy(testFile, testFileRenamed, overwrite: true);
    Thread.Sleep(SPACING);

    // Prove that if the Excel file LastWriteTime changes, we'll see it
    var excelFile = Path.Combine(appData, "ExcelTestFile.xlsx");
    var fileInfo = new FileInfo(excelFile);
    if(fileInfo.Exists)
    {
        Console.WriteLine();
        Console.WriteLine("Proves that if the Excel file LastWriteTime changes, we'll see it:");
        try
        {
            fileInfo.LastWriteTime = DateTime.Now;
        }
        catch
        {
            Console.WriteLine("CANNOT CHANGE TIMESTAMP: EXCEL FILE IS ALREADY OPEN");
        }
    }
    Thread.Sleep(SPACING);

    Console.WriteLine();
    Console.WriteLine("Waiting for Excel file changes...");
    Console.ReadKey();
}