FileSystemWatcher在保存文件之前触发 - 您如何"暂停"该过程？

Question

这是我正在尝试代码的逻辑:

服务监视目录中的.pptx文件.如果文件已更改,请执行转换为jpg.然后执行其他任务,稍后将添加.

我正在使用文件wather对象,但是一打开文件就会触发,所以我想通过检查文件是否"锁定"来停止该过程.我认为"锁定时"循环可以解决问题 - 但不是.下面是简化的代码原型,如果你能看一下,我就会知道我做错了什么和/或是否有更好的方法来为生产环境编写这个.pptx文件可以打开很长时间.

namespace FileWatcherDemo
{
   public class Program
   {

    static void Main(string[] args)
    {
        FileSystemWatcher fsWatcher = new FileSystemWatcher();
        fsWatcher.Path = @"e:\\";

        fsWatcher.NotifyFilter = NotifyFilters.LastWrite; 

        fsWatcher.Filter = "*.pptx";
        fsWatcher.Changed += new FileSystemEventHandler(fsWatcher_Changed);
        //fsWatcher.Created += new FileSystemEventHandler(fsWatcher_Changed);
        //fsWatcher.Deleted += new FileSystemEventHandler(fsWatcher_Changed);
        //fsWatcher.Renamed += new RenamedEventHandler(fsWatcher_Changed);
        fsWatcher.EnableRaisingEvents = true;
        Console.ReadKey();
    }        

    static void fsWatcher_Changed(object sender, FileSystemEventArgs e)
    {
        try
        {
            while( !IsFileLocked())
            {
                Console.WriteLine("Changed Event Fired");
                Microsoft.Office.Interop.PowerPoint.Application app = new Microsoft.Office.Interop.PowerPoint.Application();
                Presentation pptPresentation = app.Presentations.Open(@"e:\\HowTo.pptx", MsoTriState.msoFalse, MsoTriState.msoFalse, MsoTriState.msoFalse);

                pptPresentation.SaveAs(@"e:\\Output", PpSaveAsFileType.ppSaveAsJPG, MsoTriState.msoFalse);
                pptPresentation.Close();
            }
        }
        catch (Exception ex)
        {
            using (StreamWriter w = File.AppendText(@"e:\\ErrorLog.txt"))
            {
                Log(ex.Message.ToString(), w);
                Log(ex.StackTrace.ToString(), w);

                w.Close();
            }
        }

        Console.ReadKey();
    }

    static bool IsFileLocked()
    {
        FileStream fs = null;
        FileInfo file = new FileInfo(@"e:\\HowTo.pptx");            

        try
        {
            fs = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
        }
        catch (IOException)
        {
            return true;
        }
        finally
        {
            if(fs != null)
                fs.Close();
        }
        return false;
    }

    public static void Log(string LogMessage, TextWriter w)
    {
        w.Write("\r\nLog Entry: ");
        w.WriteLine("{0} {1}", DateTime.Now.ToLongTimeString(), DateTime.Now.ToLongDateString());
        w.WriteLine("  :");
        w.WriteLine("  {0}", LogMessage.ToString());
        w.WriteLine("------------------------------------------");

        w.Flush();
    }
}

}

Answer 1

这是另一种想法：当 FileSystemWatcher 检测到更改（您说它在打开文件时立即触发）时，记录文件的 LastModifiedTime 并保持循环，直到文件的 LastModifiedTime 更改（假设仅在保存文件时才写入 LastModifiedTime） - 我不知道这实际上是什么时候完成的），然后执行转换为 JPG 的过程。

编辑

添加应该演示如何跟踪文件何时被修改的代码：

class Program
{
    static void Main(string[] args)
    {
        Thread t = new Thread(()=> DoTest());
        t.Start();

        Console.WriteLine("Waiting...");
        Console.ReadKey();
    }

    private static void DoTest()
    {
        FileSystemWatcher fsw = new FileSystemWatcher("C:\\");
        fsw.Filter = "*.txt";
        fsw.Changed += new FileSystemEventHandler(fsw_Changed);
        fsw.Deleted += new FileSystemEventHandler(fsw_Deleted);
        fsw.Renamed += new RenamedEventHandler(fsw_Renamed);
        fsw.Created += new FileSystemEventHandler(fsw_Created);
        fsw.EnableRaisingEvents = true;
    }

    static void fsw_Created(object sender, FileSystemEventArgs e)
    {
        FileInfo fi = new FileInfo(e.FullPath);
        Console.WriteLine("File Created: "+e.FullPath);
        Console.WriteLine("Creation Time: " + fi.CreationTime.ToLongTimeString());
        Console.WriteLine("Last Access Time: " + fi.LastAccessTime.ToLongTimeString());
        Console.WriteLine("Last Write Time: " + fi.LastWriteTime.ToLongTimeString());
        Console.WriteLine("Length: " + fi.Length);

    }

    static void fsw_Renamed(object sender, RenamedEventArgs e)
    {
        FileInfo fi = new FileInfo(e.FullPath);
        Console.WriteLine("File Renamed: "+e.FullPath);
        Console.WriteLine("Creation Time: " + fi.CreationTime.ToLongTimeString());
        Console.WriteLine("Access Time: " + fi.LastAccessTime.ToLongTimeString());
        Console.WriteLine("Last Write Time: " + fi.LastWriteTime.ToLongTimeString());
        Console.WriteLine("Length: " + fi.Length);
    }

    static void fsw_Deleted(object sender, FileSystemEventArgs e)
    {
        FileInfo fi = new FileInfo(e.FullPath);
        Console.WriteLine("File Deleted: "+e.FullPath);
        Console.WriteLine("Creation Time: " + fi.CreationTime.ToLongTimeString());
        Console.WriteLine("Last Access Time: " + fi.LastAccessTime.ToLongTimeString());
        Console.WriteLine("Last Write Time: " + fi.LastWriteTime.ToLongTimeString());

    }

    static void fsw_Changed(object sender, FileSystemEventArgs e)
    {
        FileInfo fi = new FileInfo(e.FullPath);
        Console.WriteLine("File Changed: "+e.FullPath);
        Console.WriteLine("Creation Time: " + fi.CreationTime.ToLongTimeString());
        Console.WriteLine("Last Access Time: " + fi.LastAccessTime.ToLongTimeString());
        Console.WriteLine("Last Write Time: " + fi.LastWriteTime.ToLongTimeString());
        Console.WriteLine("Length: " + fi.Length);
    }
}