监视文件夹并查找Windows应用程序中是否打开了文件

Question

Edit: So apparently there is no simple or convenient way of knowing if a file is open / being held by a process . I think this is a problem or design decision of Windows OS itself because even programs like Process Explorer can't tell when I have "mytext.txt" file is open in notepad right besides it's window :) further research also showed only way to get this information reliably is to dvelve into system drivers. My question still stands and if anyone can show me a path to this driver solution that is also appreciated.

ps: I sincerely think there should be a simple solution to this answer. I mean, it feels like it's a feature missing in a whole OS - can't tell if a file is open? Really? Not even an API method? This doesn't feel right to me.

-- Original Question --

I've been searching all around the web to find an answer to this. Apparently after Windows Vista there is a feature called Restart Manager was added and we can invoke that dll's methods to check if a file locked or not.

However, when I try this in a simple console app (inspired by this article: https://blogs.msdn.microsoft.com/oldnewthing/20120217-00/?p=8283 and this SO answer https://stackoverflow.com/a/20623311/1858013 ) it can tell if an office file (xls, doc etc...) is locked / open but not when I open a .txt file in Notepad, or a .sln file when I have a project open in Visual Studio.

My program is monitoring a preset folder in user's system (say, Documents folder) and I want to trigger an event when any file is opened in that folder. The program itself won't modify the file or do work with that file so locking or unlocking is not a problem, I simply want to be notified when a file is opened in any program in the monitored folder.

Right now, I'm using this code to find which processes are locking a file but I feel there is an easier way to know when a file is opened than using Win32 apis.

static public class FileUtil
{
    [StructLayout(LayoutKind.Sequential)]
    struct RM_UNIQUE_PROCESS
    {
        public int dwProcessId;
        public System.Runtime.InteropServices.ComTypes.FILETIME ProcessStartTime;
    }

    const int RmRebootReasonNone = 0;
    const int CCH_RM_MAX_APP_NAME = 255;
    const int CCH_RM_MAX_SVC_NAME = 63;

    enum RM_APP_TYPE
    {
        RmUnknownApp = 0,
        RmMainWindow = 1,
        RmOtherWindow = 2,
        RmService = 3,
        RmExplorer = 4,
        RmConsole = 5,
        RmCritical = 1000
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    struct RM_PROCESS_INFO
    {
        public RM_UNIQUE_PROCESS Process;

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCH_RM_MAX_APP_NAME + 1)]
        public string strAppName;

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = CCH_RM_MAX_SVC_NAME + 1)]
        public string strServiceShortName;

        public RM_APP_TYPE ApplicationType;
        public uint AppStatus;
        public uint TSSessionId;
        [MarshalAs(UnmanagedType.Bool)]
        public bool bRestartable;
    }

    [DllImport("rstrtmgr.dll", CharSet = CharSet.Unicode)]
    static extern int RmRegisterResources(uint pSessionHandle,
                                          UInt32 nFiles,
                                          string[] rgsFilenames,
                                          UInt32 nApplications,
                                          [In] RM_UNIQUE_PROCESS[] rgApplications,
                                          UInt32 nServices,
                                          string[] rgsServiceNames);

    [DllImport("rstrtmgr.dll", CharSet = CharSet.Auto)]
    static extern int RmStartSession(out uint pSessionHandle, int dwSessionFlags, string strSessionKey);

    [DllImport("rstrtmgr.dll")]
    static extern int RmEndSession(uint pSessionHandle);

    [DllImport("rstrtmgr.dll")]
    static extern int RmGetList(uint dwSessionHandle,
                                out uint pnProcInfoNeeded,
                                ref uint pnProcInfo,
                                [In, Out] RM_PROCESS_INFO[] rgAffectedApps,
                                ref uint lpdwRebootReasons);

    /// <summary>
    /// Find out what process(es) have a lock on the specified file.
    /// </summary>
    /// <param name="path">Path of the file.</param>
    /// <returns>Processes locking the file</returns>
    /// <remarks>See also:
    /// http://msdn.microsoft.com/en-us/library/windows/desktop/aa373661(v=vs.85).aspx
    /// http://wyupdate.googlecode.com/svn-history/r401/trunk/frmFilesInUse.cs (no copyright in code at time of viewing)
    /// 
    /// </remarks>
    static public List<Process> WhoIsLocking(string path)
    {
        uint handle;
        string key = Guid.NewGuid().ToString();
        List<Process> processes = new List<Process>();

        int res = RmStartSession(out handle, 0, key);
        if (res != 0) throw new Exception("Could not begin restart session.  Unable to determine file locker.");

        try
        {
            const int ERROR_MORE_DATA = 234;
            uint pnProcInfoNeeded = 0,
                 pnProcInfo = 0,
                 lpdwRebootReasons = RmRebootReasonNone;

            string[] resources = new string[] { path }; // Just checking on one resource.

            res = RmRegisterResources(handle, (uint)resources.Length, resources, 0, null, 0, null);

            if (res != 0) throw new Exception("Could not register resource.");

            //Note: there's a race condition here -- the first call to RmGetList() returns
            //      the total number of process. However, when we call RmGetList() again to get
            //      the actual processes this number may have increased.
            res = RmGetList(handle, out pnProcInfoNeeded, ref pnProcInfo, null, ref lpdwRebootReasons);

            if (res == ERROR_MORE_DATA)
            {
                // Create an array to store the process results
                RM_PROCESS_INFO[] processInfo = new RM_PROCESS_INFO[pnProcInfoNeeded];
                pnProcInfo = pnProcInfoNeeded;

                // Get the list
                res = RmGetList(handle, out pnProcInfoNeeded, ref pnProcInfo, processInfo, ref lpdwRebootReasons);
                if (res == 0)
                {
                    processes = new List<Process>((int)pnProcInfo);

                    // Enumerate all of the results and add them to the 
                    // list to be returned
                    for (int i = 0; i < pnProcInfo; i++)
                    {
                        try
                        {
                            processes.Add(Process.GetProcessById(processInfo[i].Process.dwProcessId));
                        }
                        // catch the error -- in case the process is no longer running
                        catch (ArgumentException) { }
                    }
                }
                else throw new Exception("Could not list processes locking resource.");
            }
            else if (res != 0) throw new Exception("Could not list processes locking resource. Failed to get size of result.");
        }
        finally
        {
            RmEndSession(handle);
        }

        return processes;
    }
}

Any help would be appreciated.

Answer 1

Do you need to know who opened a file or do you just need to know if it is locked.

In case you just need to know if it is locked you can use FileSystemWatcher. This component will monitor a certain folder for various changes.