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I've seen several of answers about using Handle or Process Monitor, but I would like to be able to find out in my own code (C#) which process is locking a file.

I have a nasty feeling that I'm going to have to spelunk around in the win32 API, but if anyone has already done this and can put me on the right track, I'd really appreciate the help.

Update

Links to similar questions

Community
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AJ.
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18 Answers18

177

Long ago it was impossible to reliably get the list of processes locking a file because Windows simply did not track that information. To support the Restart Manager API, that information is now tracked.

I put together code that takes the path of a file and returns a List<Process> of all processes that are locking that file.

using System.Runtime.InteropServices;
using System.Diagnostics;
using System;
using System.Collections.Generic;

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;
    }
}

Using from Limited Permission (e.g. IIS)

This call accesses the registry. If the process does not have permission to do so, you will get ERROR_WRITE_FAULT, meaning An operation was unable to read or write to the registry. You could selectively grant permission to your restricted account to the necessary part of the registry. It is more secure though to have your limited access process set a flag (e.g. in the database or the file system, or by using an interprocess communication mechanism such as queue or named pipe) and have a second process call the Restart Manager API.

Granting other-than-minimal permissions to the IIS user is a security risk.

Waldemar Gałęzinowski
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Eric J.
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  • Has anyone tried that, it looks that it could really work (for windows above Vista and srv 2008) – Daniel Mošmondor Dec 18 '13 at 10:11
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    Is there a way to make this work for remote processes? – Carlos Muñoz Jan 24 '14 at 23:00
  • Confirmed here as well. Thanks much for posting this! +1 – ninehundreds Jun 25 '14 at 19:28
  • Is there a way to do this in WinXP? – Blagoh Aug 13 '14 at 17:53
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    @Blagoh: I do not believe the Restart Manager is available on Windows XP. You would need to resort to one of the other, less accurate methods posted here. – Eric J. Aug 13 '14 at 18:16
  • You're right its not availalbe in xp. Thanks for prompt reply. Is there any you would recommend. I like/trust your experience. Do you know about using "Runtime dynamic linking" to identify the process? Could you comment on its accuracy please. – Blagoh Aug 13 '14 at 18:51
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    @Blagoh: If you just want to know who is locking a specific DLL, you can use `tasklist /m YourDllName.dll` and parse the output. See http://stackoverflow.com/questions/152506/what-does-this-do-tasklist-m-mscor – Eric J. Aug 13 '14 at 18:58
  • Thanks for that. However it's a not a dll, its a text file. :( – Blagoh Aug 13 '14 at 19:02
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    Only solution that doesn't require 3rd party tools or undocumented API calls. Should well be the accepted answer. – IInspectable Mar 23 '15 at 15:53
  • @MichaelRayLovett: I have not seen anything about Restart Manager being depreciated. Perhaps post a simple demonstration case as a new question on Stack Overflow. Reference this question and ask what changes need to be made to get your code to work on that .NET version and Windows version. – Eric J. Mar 28 '16 at 17:30
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    I've tried this out (and it works) on Windows 2008R2, Windows 2012R2, Windows 7 and Windows 10. I found that it had to be run with elevated privileges in a lot of circumstances otherwise it fails when trying to get the list of processes locking a file. – Jay Apr 08 '16 at 12:33
  • This is fantastic. It's working on Windows 7. Thank you so much for this code. – JohnC1 Apr 26 '16 at 05:52
  • This solution works on Windows 10 however keep in mind if the program accessing said file is not putting a lock on it it'll return false. i.e: you can't tell if a .txt file is being accessed. I'm looking for a more consistent solution to this in this question: http://stackoverflow.com/questions/37276962/monitor-a-folder-and-find-if-a-file-is-open-in-windows-app – Tequilalime May 17 '16 at 15:55
  • @MichalHainc: ERROR_WRITE_FAULT means `An operation was unable to read or write to the registry.` https://msdn.microsoft.com/en-us/library/windows/desktop/aa373661(v=vs.85).aspx You *could* selectively grant permission to your IIS user to the necessary part of the registry. More secure though to have your IIS process set a flag (e.g. in the database or the file system, or by using an interprocess communication mechanism such as queue or named pipe) and have a second process call the Restart Manager API. Granting other-than-minimal permissions to the IIS user is a security risk. – Eric J. Jun 20 '16 at 17:43
  • It works on Win10 (x64) but throws exception "System.ComponentModel.Win32Exception: A 32 bit processes cannot access modules of a 64 bit process." on Win2008R2 (x64) – Alexander Selishchev Aug 16 '16 at 08:03
  • I don't understand why `RmGetList()` needs to return `ERROR_MORE_DATA` in order for it to work. It's returning 5 for me and throwing an error. – Kyle Delaney Sep 06 '17 at 21:49
  • Can't get it to work with web browsers. I need to detect if a file is open using a web browser. Is it possible ? – Anis Tissaoui Oct 16 '18 at 16:58
  • @AnisTissaoui If you mean a file on the client machine where the browser is running, not without some sort of plugin that has native access. It would be a huge security flaw if browsers gave direct file system access like that. – Eric J. Oct 17 '18 at 16:47
  • @EricJ. When it didn't work i was like "What kind of special access browsers have to the file system ?". I need to study browsers a bit more i assume. I would appreciate sharing any resources on how browsers access client machine file system :) . – Anis Tissaoui Oct 18 '18 at 11:24
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    Thank you so much. This really works for my problem. – Lake_Lagunita May 26 '21 at 09:56
  • This doesn't work for me. It shows nothing is locking the file but the I see the file being locked with lockhunter. – Gaspa79 Dec 02 '21 at 17:45
  • Does this work for 64bit? RmGetList always returns 0 for me. – Chizl Mar 20 '22 at 03:22
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    Worked perfectly on Windows 10, 64-bit. Thank you so much. – Ken Haynes Apr 15 '23 at 09:00
77

This question had an original answer that is now over 7 years old. That code is preserved at https://gist.github.com/i-e-b/2290426 This old version might work for you if you need to use Windows XP for some reason.

A much better answer is at How to check for file lock?

I've replicated Eric J's answer below (with using statements added, and class & method names to match the old code that was here) Please note that the comments to this answer may be out-of-date.

Research by user 'Walkman' is ongoing to improve the older code, as there are some conditions where the Restart Manager does not list all locks. See Github repo: https://github.com/Walkman100/FileLocks

Use like:

List<Process> locks = Win32Processes.GetProcessesLockingFile(@"C:\Hello.docx");

Code:

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace FileLockInfo
{
    public static class Win32Processes
    {
        /// <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>
        public static List<Process> GetProcessesLockingFile(string path)
        {
            uint handle;
            string key = Guid.NewGuid().ToString();
            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 MORE_DATA = 234;
                uint pnProcInfoNeeded, pnProcInfo = 0, lpdwRebootReasons = RmRebootReasonNone;

                string[] resources = {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 == MORE_DATA)
                {
                    return EnumerateProcesses(pnProcInfoNeeded, handle, lpdwRebootReasons);
                }
                else if (res != 0) throw new Exception("Could not list processes locking resource. Failed to get size of result.");
            }
            finally
            {
                RmEndSession(handle);
            }

            return new List<Process>();
        }


        [StructLayout(LayoutKind.Sequential)]
        public 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;

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

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public 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, uint nFiles, string[] rgsFilenames,
            uint nApplications, [In] RM_UNIQUE_PROCESS[] rgApplications, uint 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);

        private static List<Process> EnumerateProcesses(uint pnProcInfoNeeded, uint handle, uint lpdwRebootReasons)
        {
            var processes = new List<Process>(10);
            // Create an array to store the process results
            var processInfo = new RM_PROCESS_INFO[pnProcInfoNeeded];
            var pnProcInfo = pnProcInfoNeeded;

            // Get the list
            var res = RmGetList(handle, out pnProcInfoNeeded, ref pnProcInfo, processInfo, ref lpdwRebootReasons);

            if (res != 0) throw new Exception("Could not list processes locking resource.");
            for (int i = 0; i < pnProcInfo; i++)
            {
                try
                {
                    processes.Add(Process.GetProcessById(processInfo[i].Process.dwProcessId));
                }
                catch (ArgumentException) { } // catch the error -- in case the process is no longer running
            }
            return processes;
        }
    }
}
Iain Ballard
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  • Any idea how to fix this code from acquiring a lock of its own on files? – Boog Jun 10 '11 at 21:56
  • @Boog Could you tell me more about this bug that you've found in this code? Have you found a way to fix it yet? – Arsen Zahray Jun 20 '12 at 18:08
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    I've run this code several times, and in few of those I've got attempting to read protected memory or incorrect reading of the processes accenssing the file. It's a shame, but it does not seem that this peace of code is ready for use anywhere near production((((( – Arsen Zahray Jun 20 '12 at 23:26
  • any solution for folder locked, not file ? – Kiquenet Aug 10 '12 at 12:00
  • There are some issues with this code: 1. It doesn't work on x64. 2. `Thread.Abort` will not abort those hanging `NtQueryObject` calls anymore, so from time to time it'll hang permanently (specifically, when it hits certain named pipes which are indistinguishable from file handles). It is _still_ true that [`handle.exe` is just about the only workable approach](http://stackoverflow.com/questions/241178)... – Roman Starkov Oct 06 '12 at 13:27
  • @romkyns: Should work fine on 64 bit, but your host process will have to be 64 bit too. Yes `NtQueryObject` is buggy. Handle.exe uses the same work-arounds as everyone else (i.e. threads and drivers); @ArsenZahray: Sorry, should be a bit better now. Low-level Win32 is always a bit buggy. – Iain Ballard Oct 09 '12 at 16:58
  • @IainBallard It worked after I fiddled around with some numbers. For example, the number of entries in the handle table is 8 bytes wide on Win7 x64, not 4. The length of `SYSTEM_HANDLE_INFORMATION` is also different: Object_Pointer is IntPtr-sized. As for Handle.exe, it has the benefit of not using the .NET `Thread.Abort`, and thus can actually succeed in killing the hung `NtQueryObject`. – Roman Starkov Oct 09 '12 at 17:01
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    @romkyns would you mind sharing the final version of the code? I made the SYSTEM_HANDLE_INFORMATION change, but it won't work on my XP x64 system in either 32 or 64 mode. – Mr. TA Dec 05 '12 at 21:56
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    @Mr.TA alright, posted [an answer](http://stackoverflow.com/a/13735033/33080) with that code. But it's of little use, because it locks up occasionally. I ended up using `handle.exe`. Windows simply doesn't currently expose usable APIs to get this information; `handle.exe` is a well-tested hack. – Roman Starkov Dec 06 '12 at 00:32
  • It detects that MSWord locked a file but didn't detect my process that created a lock with System.IO.FileShare.None, is this a different kind of lock? Can it only find locks when the process leaves a ~$lockfile? – Aron Curzon Jun 17 '13 at 09:29
  • @Arsen: No code calling NtQueryObject or NtQuerySystemInformation should be going into production code, because these are internal APIs subject to change on a regular basis. – Billy ONeal Aug 07 '13 at 22:18
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    handle.exe is not an option for distributable software. See http://technet.microsoft.com/en-us/sysinternals/bb847944. – marknuzz Dec 09 '13 at 04:50
  • Take care with this code! It leaks (unmanaged) memory and other unmanaged resources. For example, the unmanaged memory allocated to `ipHandlePointer` is never freed. – mg30rg Sep 06 '17 at 15:12
  • will this detect processes on another computer that are accessing the file over the network? – user3450049 Sep 15 '18 at 09:57
  • @walkman -- added link to your research to this, as it seems to be the primary way people find this code. – Iain Ballard Apr 27 '20 at 08:30
  • Is there any way to unlock folders? – SuperBerry Aug 13 '21 at 11:53
  • @SuperBerry - I'm not aware of any directory-level lock in NTFS. I think when 'a directory or file is in use', that's a temp file opened inside the directory. – Iain Ballard Aug 13 '21 at 13:43
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    This does not work for COM ports (for example: "COM1:"), RmGetList produces a exception "Could not list processes locking resource. Failed to get size of result" – daniol Aug 25 '21 at 09:59
63

It is very complex to invoke Win32 from C#.

You should use the tool Handle.exe.

After that your C# code have to be the following:

string fileName = @"c:\aaa.doc";//Path to locked file

Process tool = new Process();
tool.StartInfo.FileName = "handle.exe";
tool.StartInfo.Arguments = fileName+" /accepteula";
tool.StartInfo.UseShellExecute = false;
tool.StartInfo.RedirectStandardOutput = true;
tool.Start();           
tool.WaitForExit();
string outputTool = tool.StandardOutput.ReadToEnd();

string matchPattern = @"(?<=\s+pid:\s+)\b(\d+)\b(?=\s+)";
foreach(Match match in Regex.Matches(outputTool, matchPattern))
{
    Process.GetProcessById(int.Parse(match.Value)).Kill();
}
Uwe Keim
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    nice example, but to my knowledge, handle.exe now shows a nasty prompt to accept some conditions when you run it on a client machine for the first time, which in my opinion, disqualifies it – Arsen Zahray Jun 20 '12 at 18:01
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    @Arsen Zahray: You can accept the eula automatically by passing in a command line option of `/accepteula`. I've updated Gennady's answer with the change. – Jon Cage Oct 18 '12 at 15:08
  • What version of Handle.exe did you use? The newest one V4 seems to be changed in a Broken way. /accepteula and Filename is not longer supported – Venson Sep 24 '14 at 13:41
  • @JPVenson: I just tried the latest version available for download (v4.0 Published: September 11, 2014) and /accepteula and filename both work fine. – Mr. Bungle Oct 10 '14 at 02:04
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    You can't redistribute `handle.exe` – Basic Mar 05 '15 at 03:14
  • You can download it on the fly, tough. Also, you can write the `EulaAccepted` value inside `HKCU\Software\Sysinternals\` in the windows registry prior to running, thus avoiding an unnecessary program run. – beppe9000 Aug 24 '15 at 19:13
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    I disagree - it has no complexity when invoking win32 api from c#. – Idan Oct 13 '15 at 16:53
  • add this line: fileName = "\"" + fileName + "\""; this will allow spaces in the dir, – DarkPh03n1X Jan 17 '17 at 08:53
  • add this line: tool.StartInfo.CreateNoWindow = true; this will hide the black box – DarkPh03n1X Jan 17 '17 at 08:53
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    This is really slow for me. Did anyone find a faster way of doing this? Especially for multiple files? – DeveloperExceptionError Mar 03 '20 at 15:29
38

One of the good things about handle.exe is that you can run it as a subprocess and parse the output.

We do this in our deployment script - works like a charm.

orip
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20

The code I found here, https://vmccontroller.svn.codeplex.com/svn/VmcController/VmcServices/DetectOpenFiles.cs

Works for me much better than the code provided by Iain. Iain's code seemed to be acquiring a lock of its own. Here is my slightly modified version of the code above modified to return the string path of the files locked instead of the FileSystemInfo object,

using System;
using System.Collections.Generic;
//using System.EnterpriseServices;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;
using System.Security.Permissions;
using System.Text;
using System.Threading;
using Microsoft.Win32.SafeHandles;

namespace Crmc.Core.BuildTasks
{
    using System.Diagnostics;
    using System.Linq;

    #region ENUMs
    internal enum NT_STATUS
    {
        STATUS_SUCCESS = 0x00000000,
        STATUS_BUFFER_OVERFLOW = unchecked((int)0x80000005L),
        STATUS_INFO_LENGTH_MISMATCH = unchecked((int)0xC0000004L)
    }

    internal enum SYSTEM_INFORMATION_CLASS
    {
        SystemBasicInformation = 0,
        SystemPerformanceInformation = 2,
        SystemTimeOfDayInformation = 3,
        SystemProcessInformation = 5,
        SystemProcessorPerformanceInformation = 8,
        SystemHandleInformation = 16,
        SystemInterruptInformation = 23,
        SystemExceptionInformation = 33,
        SystemRegistryQuotaInformation = 37,
        SystemLookasideInformation = 45
    }

    internal enum OBJECT_INFORMATION_CLASS
    {
        ObjectBasicInformation = 0,
        ObjectNameInformation = 1,
        ObjectTypeInformation = 2,
        ObjectAllTypesInformation = 3,
        ObjectHandleInformation = 4
    }

    [Flags]
    internal enum ProcessAccessRights
    {
        PROCESS_DUP_HANDLE = 0x00000040
    }

    [Flags]
    internal enum DuplicateHandleOptions
    {
        DUPLICATE_CLOSE_SOURCE = 0x1,
        DUPLICATE_SAME_ACCESS = 0x2
    }
    #endregion

    [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
    internal sealed class SafeObjectHandle : SafeHandleZeroOrMinusOneIsInvalid
    {
        private SafeObjectHandle()
            : base(true)
        { }

        internal SafeObjectHandle(IntPtr preexistingHandle, bool ownsHandle)
            : base(ownsHandle)
        {
            base.SetHandle(preexistingHandle);
        }

        protected override bool ReleaseHandle()
        {
            return NativeMethods.CloseHandle(base.handle);
        }
    }

    [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode = true)]
    internal sealed class SafeProcessHandle : SafeHandleZeroOrMinusOneIsInvalid
    {
        private SafeProcessHandle()
            : base(true)
        { }

        internal SafeProcessHandle(IntPtr preexistingHandle, bool ownsHandle)
            : base(ownsHandle)
        {
            base.SetHandle(preexistingHandle);
        }

        protected override bool ReleaseHandle()
        {
            return NativeMethods.CloseHandle(base.handle);
        }
    }

    #region Native Methods
    internal static class NativeMethods
    {
        [DllImport("ntdll.dll")]
        internal static extern NT_STATUS NtQuerySystemInformation(
            [In] SYSTEM_INFORMATION_CLASS SystemInformationClass,
            [In] IntPtr SystemInformation,
            [In] int SystemInformationLength,
            [Out] out int ReturnLength);

        [DllImport("ntdll.dll")]
        internal static extern NT_STATUS NtQueryObject(
            [In] IntPtr Handle,
            [In] OBJECT_INFORMATION_CLASS ObjectInformationClass,
            [In] IntPtr ObjectInformation,
            [In] int ObjectInformationLength,
            [Out] out int ReturnLength);

        [DllImport("kernel32.dll", SetLastError = true)]
        internal static extern SafeProcessHandle OpenProcess(
            [In] ProcessAccessRights dwDesiredAccess,
            [In, MarshalAs(UnmanagedType.Bool)] bool bInheritHandle,
            [In] int dwProcessId);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        internal static extern bool DuplicateHandle(
            [In] IntPtr hSourceProcessHandle,
            [In] IntPtr hSourceHandle,
            [In] IntPtr hTargetProcessHandle,
            [Out] out SafeObjectHandle lpTargetHandle,
            [In] int dwDesiredAccess,
            [In, MarshalAs(UnmanagedType.Bool)] bool bInheritHandle,
            [In] DuplicateHandleOptions dwOptions);

        [DllImport("kernel32.dll")]
        internal static extern IntPtr GetCurrentProcess();

        [DllImport("kernel32.dll", SetLastError = true)]
        internal static extern int GetProcessId(
            [In] IntPtr Process);

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        internal static extern bool CloseHandle(
            [In] IntPtr hObject);

        [DllImport("kernel32.dll", SetLastError = true)]
        internal static extern int QueryDosDevice(
            [In] string lpDeviceName,
            [Out] StringBuilder lpTargetPath,
            [In] int ucchMax);
    }
    #endregion

    //[ComVisible(true), EventTrackingEnabled(true)]
    public class DetectOpenFiles// : ServicedComponent
    {
        private static Dictionary<string, string> deviceMap;
        private const string networkDevicePrefix = "\\Device\\LanmanRedirector\\";

        private const int MAX_PATH = 260;

        private enum SystemHandleType
        {
            OB_TYPE_UNKNOWN = 0,
            OB_TYPE_TYPE = 1,
            OB_TYPE_DIRECTORY,
            OB_TYPE_SYMBOLIC_LINK,
            OB_TYPE_TOKEN,
            OB_TYPE_PROCESS,
            OB_TYPE_THREAD,
            OB_TYPE_UNKNOWN_7,
            OB_TYPE_EVENT,
            OB_TYPE_EVENT_PAIR,
            OB_TYPE_MUTANT,
            OB_TYPE_UNKNOWN_11,
            OB_TYPE_SEMAPHORE,
            OB_TYPE_TIMER,
            OB_TYPE_PROFILE,
            OB_TYPE_WINDOW_STATION,
            OB_TYPE_DESKTOP,
            OB_TYPE_SECTION,
            OB_TYPE_KEY,
            OB_TYPE_PORT,
            OB_TYPE_WAITABLE_PORT,
            OB_TYPE_UNKNOWN_21,
            OB_TYPE_UNKNOWN_22,
            OB_TYPE_UNKNOWN_23,
            OB_TYPE_UNKNOWN_24,
            //OB_TYPE_CONTROLLER,
            //OB_TYPE_DEVICE,
            //OB_TYPE_DRIVER,
            OB_TYPE_IO_COMPLETION,
            OB_TYPE_FILE
        };

        private const int handleTypeTokenCount = 27;
        private static readonly string[] handleTypeTokens = new string[] { 
            "", "", "Directory", "SymbolicLink", "Token",
            "Process", "Thread", "Unknown7", "Event", "EventPair", "Mutant",
            "Unknown11", "Semaphore", "Timer", "Profile", "WindowStation",
            "Desktop", "Section", "Key", "Port", "WaitablePort",
            "Unknown21", "Unknown22", "Unknown23", "Unknown24", 
            "IoCompletion", "File"
        };

        [StructLayout(LayoutKind.Sequential)]
        private struct SYSTEM_HANDLE_ENTRY
        {
            public int OwnerPid;
            public byte ObjectType;
            public byte HandleFlags;
            public short HandleValue;
            public int ObjectPointer;
            public int AccessMask;
        }

        /// <summary>
        /// Gets the open files enumerator.
        /// </summary>
        /// <param name="processId">The process id.</param>
        /// <returns></returns>
        public static IEnumerable<String> GetOpenFilesEnumerator(int processId)
        {
            return new OpenFiles(processId);
        }

        public static List<Process> GetProcessesUsingFile(string fName)
        {
            List<Process> result = new List<Process>();
            foreach (var p in Process.GetProcesses())
            {
                try
                {
                    if (DetectOpenFiles.GetOpenFilesEnumerator(p.Id).Contains(fName))
                    {
                        result.Add(p);
                    }
                }
                catch { }//some processes will fail
            }
            return result;
        }

        private sealed class OpenFiles : IEnumerable<String>
        {
            private readonly int processId;

            internal OpenFiles(int processId)
            {
                this.processId = processId;
            }

            #region IEnumerable<FileSystemInfo> Members

            public IEnumerator<String> GetEnumerator()
            {
                NT_STATUS ret;
                int length = 0x10000;
                // Loop, probing for required memory.


                do
                {
                    IntPtr ptr = IntPtr.Zero;
                    RuntimeHelpers.PrepareConstrainedRegions();
                    try
                    {
                        RuntimeHelpers.PrepareConstrainedRegions();
                        try { }
                        finally
                        {
                            // CER guarantees that the address of the allocated 
                            // memory is actually assigned to ptr if an 
                            // asynchronous exception occurs.
                            ptr = Marshal.AllocHGlobal(length);
                        }
                        int returnLength;
                        ret = NativeMethods.NtQuerySystemInformation(SYSTEM_INFORMATION_CLASS.SystemHandleInformation, ptr, length, out returnLength);
                        if (ret == NT_STATUS.STATUS_INFO_LENGTH_MISMATCH)
                        {
                            // Round required memory up to the nearest 64KB boundary.
                            length = ((returnLength + 0xffff) & ~0xffff);
                        }
                        else if (ret == NT_STATUS.STATUS_SUCCESS)
                        {
                            int handleCount = Marshal.ReadInt32(ptr);
                            int offset = sizeof(int);
                            int size = Marshal.SizeOf(typeof(SYSTEM_HANDLE_ENTRY));
                            for (int i = 0; i < handleCount; i++)
                            {
                                SYSTEM_HANDLE_ENTRY handleEntry = (SYSTEM_HANDLE_ENTRY)Marshal.PtrToStructure((IntPtr)((int)ptr + offset), typeof(SYSTEM_HANDLE_ENTRY));
                                if (handleEntry.OwnerPid == processId)
                                {
                                    IntPtr handle = (IntPtr)handleEntry.HandleValue;
                                    SystemHandleType handleType;

                                    if (GetHandleType(handle, handleEntry.OwnerPid, out handleType) && handleType == SystemHandleType.OB_TYPE_FILE)
                                    {
                                        string devicePath;
                                        if (GetFileNameFromHandle(handle, handleEntry.OwnerPid, out devicePath))
                                        {
                                            string dosPath;
                                            if (ConvertDevicePathToDosPath(devicePath, out dosPath))
                                            {
                                                if (File.Exists(dosPath))
                                                {
                                                    yield return dosPath; // return new FileInfo(dosPath);
                                                }
                                                else if (Directory.Exists(dosPath))
                                                {
                                                    yield return dosPath; // new DirectoryInfo(dosPath);
                                                }
                                            }
                                        }
                                    }
                                }
                                offset += size;
                            }
                        }
                    }
                    finally
                    {
                        // CER guarantees that the allocated memory is freed, 
                        // if an asynchronous exception occurs. 
                        Marshal.FreeHGlobal(ptr);
                        //sw.Flush();
                        //sw.Close();
                    }
                }
                while (ret == NT_STATUS.STATUS_INFO_LENGTH_MISMATCH);
            }

            #endregion

            #region IEnumerable Members

            System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
            {
                return GetEnumerator();
            }

            #endregion
        }

        #region Private Members

        private static bool GetFileNameFromHandle(IntPtr handle, int processId, out string fileName)
        {
            IntPtr currentProcess = NativeMethods.GetCurrentProcess();
            bool remote = (processId != NativeMethods.GetProcessId(currentProcess));
            SafeProcessHandle processHandle = null;
            SafeObjectHandle objectHandle = null;
            try
            {
                if (remote)
                {
                    processHandle = NativeMethods.OpenProcess(ProcessAccessRights.PROCESS_DUP_HANDLE, true, processId);
                    if (NativeMethods.DuplicateHandle(processHandle.DangerousGetHandle(), handle, currentProcess, out objectHandle, 0, false, DuplicateHandleOptions.DUPLICATE_SAME_ACCESS))
                    {
                        handle = objectHandle.DangerousGetHandle();
                    }
                }
                return GetFileNameFromHandle(handle, out fileName, 200);
            }
            finally
            {
                if (remote)
                {
                    if (processHandle != null)
                    {
                        processHandle.Close();
                    }
                    if (objectHandle != null)
                    {
                        objectHandle.Close();
                    }
                }
            }
        }
        private static bool GetFileNameFromHandle(IntPtr handle, out string fileName, int wait)
        {
            using (FileNameFromHandleState f = new FileNameFromHandleState(handle))
            {
                ThreadPool.QueueUserWorkItem(new WaitCallback(GetFileNameFromHandle), f);
                if (f.WaitOne(wait))
                {
                    fileName = f.FileName;
                    return f.RetValue;
                }
                else
                {
                    fileName = string.Empty;
                    return false;
                }
            }
        }

        private class FileNameFromHandleState : IDisposable
        {
            private ManualResetEvent _mr;
            private IntPtr _handle;
            private string _fileName;
            private bool _retValue;

            public IntPtr Handle
            {
                get
                {
                    return _handle;
                }
            }

            public string FileName
            {
                get
                {
                    return _fileName;
                }
                set
                {
                    _fileName = value;
                }

            }

            public bool RetValue
            {
                get
                {
                    return _retValue;
                }
                set
                {
                    _retValue = value;
                }
            }

            public FileNameFromHandleState(IntPtr handle)
            {
                _mr = new ManualResetEvent(false);
                this._handle = handle;
            }

            public bool WaitOne(int wait)
            {
                return _mr.WaitOne(wait, false);
            }

            public void Set()
            {
                try
                {
                    _mr.Set();
                }
                catch{}
            }
            #region IDisposable Members

            public void Dispose()
            {
                if (_mr != null)
                    _mr.Close();
            }

            #endregion
        }

        private static void GetFileNameFromHandle(object state)
        {
            FileNameFromHandleState s = (FileNameFromHandleState)state;
            string fileName;
            s.RetValue = GetFileNameFromHandle(s.Handle, out fileName);
            s.FileName = fileName;
            s.Set();
        }

        private static bool GetFileNameFromHandle(IntPtr handle, out string fileName)
        {
            IntPtr ptr = IntPtr.Zero;
            RuntimeHelpers.PrepareConstrainedRegions();
            try
            {
                int length = 0x200;  // 512 bytes
                RuntimeHelpers.PrepareConstrainedRegions();
                try { }
                finally
                {
                    // CER guarantees the assignment of the allocated 
                    // memory address to ptr, if an ansynchronous exception 
                    // occurs.
                    ptr = Marshal.AllocHGlobal(length);
                }
                NT_STATUS ret = NativeMethods.NtQueryObject(handle, OBJECT_INFORMATION_CLASS.ObjectNameInformation, ptr, length, out length);
                if (ret == NT_STATUS.STATUS_BUFFER_OVERFLOW)
                {
                    RuntimeHelpers.PrepareConstrainedRegions();
                    try { }
                    finally
                    {
                        // CER guarantees that the previous allocation is freed,
                        // and that the newly allocated memory address is 
                        // assigned to ptr if an asynchronous exception occurs.
                        Marshal.FreeHGlobal(ptr);
                        ptr = Marshal.AllocHGlobal(length);
                    }
                    ret = NativeMethods.NtQueryObject(handle, OBJECT_INFORMATION_CLASS.ObjectNameInformation, ptr, length, out length);
                }
                if (ret == NT_STATUS.STATUS_SUCCESS)
                {
                    fileName = Marshal.PtrToStringUni((IntPtr)((int)ptr + 8), (length - 9) / 2);
                    return fileName.Length != 0;
                }
            }
            finally
            {
                // CER guarantees that the allocated memory is freed, 
                // if an asynchronous exception occurs.
                Marshal.FreeHGlobal(ptr);
            }

            fileName = string.Empty;
            return false;
        }

        private static bool GetHandleType(IntPtr handle, int processId, out SystemHandleType handleType)
        {
            string token = GetHandleTypeToken(handle, processId);
            return GetHandleTypeFromToken(token, out handleType);
        }

        private static bool GetHandleType(IntPtr handle, out SystemHandleType handleType)
        {
            string token = GetHandleTypeToken(handle);
            return GetHandleTypeFromToken(token, out handleType);
        }

        private static bool GetHandleTypeFromToken(string token, out SystemHandleType handleType)
        {
            for (int i = 1; i < handleTypeTokenCount; i++)
            {
                if (handleTypeTokens[i] == token)
                {
                    handleType = (SystemHandleType)i;
                    return true;
                }
            }
            handleType = SystemHandleType.OB_TYPE_UNKNOWN;
            return false;
        }

        private static string GetHandleTypeToken(IntPtr handle, int processId)
        {
            IntPtr currentProcess = NativeMethods.GetCurrentProcess();
            bool remote = (processId != NativeMethods.GetProcessId(currentProcess));
            SafeProcessHandle processHandle = null;
            SafeObjectHandle objectHandle = null;
            try
            {
                if (remote)
                {
                    processHandle = NativeMethods.OpenProcess(ProcessAccessRights.PROCESS_DUP_HANDLE, true, processId);
                    if (NativeMethods.DuplicateHandle(processHandle.DangerousGetHandle(), handle, currentProcess, out objectHandle, 0, false, DuplicateHandleOptions.DUPLICATE_SAME_ACCESS))
                    {
                        handle = objectHandle.DangerousGetHandle();
                    }
                }
                return GetHandleTypeToken(handle);
            }
            finally
            {
                if (remote)
                {
                    if (processHandle != null)
                    {
                        processHandle.Close();
                    }
                    if (objectHandle != null)
                    {
                        objectHandle.Close();
                    }
                }
            }
        }

        private static string GetHandleTypeToken(IntPtr handle)
        {
            int length;
            NativeMethods.NtQueryObject(handle, OBJECT_INFORMATION_CLASS.ObjectTypeInformation, IntPtr.Zero, 0, out length);
            IntPtr ptr = IntPtr.Zero;
            RuntimeHelpers.PrepareConstrainedRegions();
            try
            {
                RuntimeHelpers.PrepareConstrainedRegions();
                try { }
                finally
                {
                    ptr = Marshal.AllocHGlobal(length);
                }
                if (NativeMethods.NtQueryObject(handle, OBJECT_INFORMATION_CLASS.ObjectTypeInformation, ptr, length, out length) == NT_STATUS.STATUS_SUCCESS)
                {
                    return Marshal.PtrToStringUni((IntPtr)((int)ptr + 0x60));
                }
            }
            finally
            {
                Marshal.FreeHGlobal(ptr);
            }
            return string.Empty;
        }

        private static bool ConvertDevicePathToDosPath(string devicePath, out string dosPath)
        {
            EnsureDeviceMap();
            int i = devicePath.Length;
            while (i > 0 && (i = devicePath.LastIndexOf('\\', i - 1)) != -1)
            {
                string drive;
                if (deviceMap.TryGetValue(devicePath.Substring(0, i), out drive))
                {
                    dosPath = string.Concat(drive, devicePath.Substring(i));
                    return dosPath.Length != 0;
                }
            }
            dosPath = string.Empty;
            return false;
        }

        private static void EnsureDeviceMap()
        {
            if (deviceMap == null)
            {
                Dictionary<string, string> localDeviceMap = BuildDeviceMap();
                Interlocked.CompareExchange<Dictionary<string, string>>(ref deviceMap, localDeviceMap, null);
            }
        }

        private static Dictionary<string, string> BuildDeviceMap()
        {
            string[] logicalDrives = Environment.GetLogicalDrives();
            Dictionary<string, string> localDeviceMap = new Dictionary<string, string>(logicalDrives.Length);
            StringBuilder lpTargetPath = new StringBuilder(MAX_PATH);
            foreach (string drive in logicalDrives)
            {
                string lpDeviceName = drive.Substring(0, 2);
                NativeMethods.QueryDosDevice(lpDeviceName, lpTargetPath, MAX_PATH);
                localDeviceMap.Add(NormalizeDeviceName(lpTargetPath.ToString()), lpDeviceName);
            }
            localDeviceMap.Add(networkDevicePrefix.Substring(0, networkDevicePrefix.Length - 1), "\\");
            return localDeviceMap;
        }

        private static string NormalizeDeviceName(string deviceName)
        {
            if (string.Compare(deviceName, 0, networkDevicePrefix, 0, networkDevicePrefix.Length, StringComparison.InvariantCulture) == 0)
            {
                string shareName = deviceName.Substring(deviceName.IndexOf('\\', networkDevicePrefix.Length) + 1);
                return string.Concat(networkDevicePrefix, shareName);
            }
            return deviceName;
        }

        #endregion
    }
}
Arsen Zahray
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Boog
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15

Not very straightforward, but on Windows Vista and above you can use the Restart Manager APIs to see who is using a file. Internet Explorer caches settings includes details on using this to detect which process has iexplore.exe open.

Omitting a lot of detail:

// Start an RM session
RmStartSession(&sessionHandle, 0, sessionKey);

// Register the file you are checking
RmRegisterResources(sessionHandle, 1, filePathArray, 0, NULL, 0, NULL);

// Get all processes that have that file open.
RmGetList(sessionHAndle, &nProcInfoNeeded, &nProcInfo, processes, &rebootReason);
RmEndSession(sessionHandle);
Peter Mortensen
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Michael
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    Thanks for this. Here's also a good article on the Restart Manager topic: http://msdn.microsoft.com/en-us/magazine/cc163450.aspx. Detailed here is a method for getting processes that use a file. – Michael Detras May 30 '11 at 07:44
  • 1
    This really should be the accepted answer. It's the only solution that doesn't use 3rd party tools or undocumented APIs. – IInspectable Mar 23 '15 at 15:47
  • WARNING: this only works in desktop apps, not for example on windows services. – gigi Feb 11 '16 at 12:09
  • @gigi: What's the error mode for services? What error codes are returned? Seeing that the *Restart Manager* API is primarily used with installers, and there's no issue running installers from a service, I would be surprised to find out, that the Restart Manager wouldn't work from a service. – IInspectable Aug 23 '16 at 10:44
  • @IInspectable: If you go to the MSDN page of the Restart Manager API linked above, you can read: "Restart Manager is intended for the development of desktop style applications." Your example it's not an exception. What I mean is that you can't use the API from a c# windows service application. That won't work. But of course you can start a separate desktop executable from the service. That might work. – gigi Aug 23 '16 at 11:07
9

I had issues with stefan's solution. Below is a modified version which seems to work well.

using System;
using System.Collections;
using System.Diagnostics;
using System.Management;
using System.IO;

static class Module1
{
    static internal ArrayList myProcessArray = new ArrayList();
    private static Process myProcess;

    public static void Main()
    {
        string strFile = "c:\\windows\\system32\\msi.dll";
        ArrayList a = getFileProcesses(strFile);
        foreach (Process p in a)
        {
            Debug.Print(p.ProcessName);
        }
    }

    private static ArrayList getFileProcesses(string strFile)
    {
        myProcessArray.Clear();
        Process[] processes = Process.GetProcesses();
        int i = 0;
        for (i = 0; i <= processes.GetUpperBound(0) - 1; i++)
        {
            myProcess = processes[i];
            //if (!myProcess.HasExited) //This will cause an "Access is denied" error
            if (myProcess.Threads.Count > 0)
            {
                try
                {
                    ProcessModuleCollection modules = myProcess.Modules;
                    int j = 0;
                    for (j = 0; j <= modules.Count - 1; j++)
                    {
                        if ((modules[j].FileName.ToLower().CompareTo(strFile.ToLower()) == 0))
                        {
                            myProcessArray.Add(myProcess);
                            break;
                            // TODO: might not be correct. Was : Exit For
                        }
                    }
                }
                catch (Exception exception)
                {
                    //MsgBox(("Error : " & exception.Message)) 
                }
            }
        }

        return myProcessArray;
    }
}

UPDATE

If you just want to know which process(es) are locking a particular DLL, you can execute and parse the output of tasklist /m YourDllName.dll. Works on Windows XP and later. See

What does this do? tasklist /m "mscor*"

Community
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user137604
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  • I so very much fail to see why `myProcessArray` is a class member (but also actually returned from getFileProcesses()? Same goes for `myProcess`. – Oskar Berggren Nov 20 '17 at 08:31
9

Handle, from Windows Sysinternals. This is a free command-line utility provided by Microsoft.

You could run it, and parse the result.

Peter Mortensen
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Daniel Silveira
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  • This is not what the OP asked for – Trap May 13 '09 at 22:09
  • @Trap What the problem with my answer? Do you know this utility? – Daniel Silveira May 13 '09 at 22:12
  • 3
    Not sure running a 3rd party tool and parsing output counts as "programatically". – Michael May 13 '09 at 22:20
  • Well, if you can write a program that executes the 3rd party tool (you can) and parses the output (you can) then I'd say that's programmatic. Albeit, not quite what the OP was looking for. – DevinB May 13 '09 at 22:25
  • 5
    @Daniel You need to have it installed, have administrative privileges and rely on the user interface output. Can't think of a less elegant solution let alone a 'programmatical' one. – Trap May 13 '09 at 22:45
  • 1
    Sometimes integrating a third party tool is necessary. It saves the effort of trying to rewrite code that someone else has already written. You can easily package up the exe with your own deployment package. – DevinB May 13 '09 at 22:48
  • 1
    I wouldn't consider it a 3rd app, since it is provided by Microsoft Itself. Anyway, do you have a better approach? – Daniel Silveira May 13 '09 at 23:54
  • 1
    It's ok to use any valid solution you might see easy. I prefer to stick with .NET Framework defaults. 3rd party app is in general my last resort – Junior Mayhé May 24 '10 at 18:53
7

This works for DLLs locked by other processes. This routine will not find out for example that a text file is locked by a word process.

C#:

using System.Management; 
using System.IO;   

static class Module1 
{ 
static internal ArrayList myProcessArray = new ArrayList(); 
private static Process myProcess; 

public static void Main() 
{ 

    string strFile = "c:\\windows\\system32\\msi.dll"; 
    ArrayList a = getFileProcesses(strFile); 
    foreach (Process p in a) { 
        Debug.Print(p.ProcessName); 
    } 
} 


private static ArrayList getFileProcesses(string strFile) 
{ 
    myProcessArray.Clear(); 
    Process[] processes = Process.GetProcesses; 
    int i = 0; 
    for (i = 0; i <= processes.GetUpperBound(0) - 1; i++) { 
        myProcess = processes(i); 
        if (!myProcess.HasExited) { 
            try { 
                ProcessModuleCollection modules = myProcess.Modules; 
                int j = 0; 
                for (j = 0; j <= modules.Count - 1; j++) { 
                    if ((modules.Item(j).FileName.ToLower.CompareTo(strFile.ToLower) == 0)) { 
                        myProcessArray.Add(myProcess); 
                        break; // TODO: might not be correct. Was : Exit For 
                    } 
                } 
            } 
            catch (Exception exception) { 
            } 
            //MsgBox(("Error : " & exception.Message)) 
        } 
    } 
    return myProcessArray; 
} 
} 

VB.Net:

Imports System.Management
Imports System.IO

Module Module1
Friend myProcessArray As New ArrayList
Private myProcess As Process

Sub Main()

    Dim strFile As String = "c:\windows\system32\msi.dll"
    Dim a As ArrayList = getFileProcesses(strFile)
    For Each p As Process In a
        Debug.Print(p.ProcessName)
    Next
End Sub


Private Function getFileProcesses(ByVal strFile As String) As ArrayList
    myProcessArray.Clear()
    Dim processes As Process() = Process.GetProcesses
    Dim i As Integer
    For i = 0 To processes.GetUpperBound(0) - 1
        myProcess = processes(i)
        If Not myProcess.HasExited Then
            Try
                Dim modules As ProcessModuleCollection = myProcess.Modules
                Dim j As Integer
                For j = 0 To modules.Count - 1
                    If (modules.Item(j).FileName.ToLower.CompareTo(strFile.ToLower) = 0) Then
                        myProcessArray.Add(myProcess)
                        Exit For
                    End If
                Next j
            Catch exception As Exception
                'MsgBox(("Error : " & exception.Message))
            End Try
        End If
    Next i
    Return myProcessArray
End Function
End Module
phuclv
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Stefan
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5

The following was produced based on Iain Ballard's code dump. It is broken: it will occasionally lock up when you retrieve the handle name. This code doesn't contain any work-arounds for that issue, and .NET leaves few options: Thread.Abort can no longer abort a thread that's currently in a native method.

So, with that disclaimer, here is the code to retrieve handles which has been adapted to work (apart from the occasional lock-up) both in 32 and 64 bit modes:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.ConstrainedExecution;
using System.Runtime.InteropServices;

namespace BrokenHandleRetrieval
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Enumerates open handles.");
            Console.WriteLine("This *will* lock up on calling HandleInfo.Name from time to time. Thread.Abort() won't help.");
            foreach (var hi in HandleUtil.GetHandles().Where(hi => hi.Type == HandleType.File))
                Console.WriteLine("pid: " + hi.ProcessId + ", name: " + hi.Name);
        }
    }

    public enum HandleType
    {
        Unknown,
        Other,
        File, Directory, SymbolicLink, Key,
        Process, Thread, Job, Session, WindowStation,
        Timer, Desktop, Semaphore, Token,
        Mutant, Section, Event, KeyedEvent, IoCompletion, IoCompletionReserve,
        TpWorkerFactory, AlpcPort, WmiGuid, UserApcReserve,
    }

    public class HandleInfo
    {
        public int ProcessId { get; private set; }
        public ushort Handle { get; private set; }
        public int GrantedAccess { get; private set; }
        public byte RawType { get; private set; }

        public HandleInfo(int processId, ushort handle, int grantedAccess, byte rawType)
        {
            ProcessId = processId;
            Handle = handle;
            GrantedAccess = grantedAccess;
            RawType = rawType;
        }

        private static Dictionary<byte, string> _rawTypeMap = new Dictionary<byte, string>();

        private string _name, _typeStr;
        private HandleType _type;

        public string Name { get { if (_name == null) initTypeAndName(); return _name; } }
        public string TypeString { get { if (_typeStr == null) initType(); return _typeStr; } }
        public HandleType Type { get { if (_typeStr == null) initType(); return _type; } }

        private void initType()
        {
            if (_rawTypeMap.ContainsKey(RawType))
            {
                _typeStr = _rawTypeMap[RawType];
                _type = HandleTypeFromString(_typeStr);
            }
            else
                initTypeAndName();
        }

        bool _typeAndNameAttempted = false;

        private void initTypeAndName()
        {
            if (_typeAndNameAttempted)
                return;
            _typeAndNameAttempted = true;

            IntPtr sourceProcessHandle = IntPtr.Zero;
            IntPtr handleDuplicate = IntPtr.Zero;
            try
            {
                sourceProcessHandle = NativeMethods.OpenProcess(0x40 /* dup_handle */, true, ProcessId);

                // To read info about a handle owned by another process we must duplicate it into ours
                // For simplicity, current process handles will also get duplicated; remember that process handles cannot be compared for equality
                if (!NativeMethods.DuplicateHandle(sourceProcessHandle, (IntPtr) Handle, NativeMethods.GetCurrentProcess(), out handleDuplicate, 0, false, 2 /* same_access */))
                    return;

                // Query the object type
                if (_rawTypeMap.ContainsKey(RawType))
                    _typeStr = _rawTypeMap[RawType];
                else
                {
                    int length;
                    NativeMethods.NtQueryObject(handleDuplicate, OBJECT_INFORMATION_CLASS.ObjectTypeInformation, IntPtr.Zero, 0, out length);
                    IntPtr ptr = IntPtr.Zero;
                    try
                    {
                        ptr = Marshal.AllocHGlobal(length);
                        if (NativeMethods.NtQueryObject(handleDuplicate, OBJECT_INFORMATION_CLASS.ObjectTypeInformation, ptr, length, out length) != NT_STATUS.STATUS_SUCCESS)
                            return;
                        _typeStr = Marshal.PtrToStringUni((IntPtr) ((int) ptr + 0x58 + 2 * IntPtr.Size));
                        _rawTypeMap[RawType] = _typeStr;
                    }
                    finally
                    {
                        Marshal.FreeHGlobal(ptr);
                    }
                }
                _type = HandleTypeFromString(_typeStr);

                // Query the object name
                if (_typeStr != null && GrantedAccess != 0x0012019f && GrantedAccess != 0x00120189 && GrantedAccess != 0x120089) // don't query some objects that could get stuck
                {
                    int length;
                    NativeMethods.NtQueryObject(handleDuplicate, OBJECT_INFORMATION_CLASS.ObjectNameInformation, IntPtr.Zero, 0, out length);
                    IntPtr ptr = IntPtr.Zero;
                    try
                    {
                        ptr = Marshal.AllocHGlobal(length);
                        if (NativeMethods.NtQueryObject(handleDuplicate, OBJECT_INFORMATION_CLASS.ObjectNameInformation, ptr, length, out length) != NT_STATUS.STATUS_SUCCESS)
                            return;
                        _name = Marshal.PtrToStringUni((IntPtr) ((int) ptr + 2 * IntPtr.Size));
                    }
                    finally
                    {
                        Marshal.FreeHGlobal(ptr);
                    }
                }
            }
            finally
            {
                NativeMethods.CloseHandle(sourceProcessHandle);
                if (handleDuplicate != IntPtr.Zero)
                    NativeMethods.CloseHandle(handleDuplicate);
            }
        }

        public static HandleType HandleTypeFromString(string typeStr)
        {
            switch (typeStr)
            {
                case null: return HandleType.Unknown;
                case "File": return HandleType.File;
                case "IoCompletion": return HandleType.IoCompletion;
                case "TpWorkerFactory": return HandleType.TpWorkerFactory;
                case "ALPC Port": return HandleType.AlpcPort;
                case "Event": return HandleType.Event;
                case "Section": return HandleType.Section;
                case "Directory": return HandleType.Directory;
                case "KeyedEvent": return HandleType.KeyedEvent;
                case "Process": return HandleType.Process;
                case "Key": return HandleType.Key;
                case "SymbolicLink": return HandleType.SymbolicLink;
                case "Thread": return HandleType.Thread;
                case "Mutant": return HandleType.Mutant;
                case "WindowStation": return HandleType.WindowStation;
                case "Timer": return HandleType.Timer;
                case "Semaphore": return HandleType.Semaphore;
                case "Desktop": return HandleType.Desktop;
                case "Token": return HandleType.Token;
                case "Job": return HandleType.Job;
                case "Session": return HandleType.Session;
                case "IoCompletionReserve": return HandleType.IoCompletionReserve;
                case "WmiGuid": return HandleType.WmiGuid;
                case "UserApcReserve": return HandleType.UserApcReserve;
                default: return HandleType.Other;
            }
        }
    }

    public static class HandleUtil
    {
        public static IEnumerable<HandleInfo> GetHandles()
        {
            // Attempt to retrieve the handle information
            int length = 0x10000;
            IntPtr ptr = IntPtr.Zero;
            try
            {
                while (true)
                {
                    ptr = Marshal.AllocHGlobal(length);
                    int wantedLength;
                    var result = NativeMethods.NtQuerySystemInformation(SYSTEM_INFORMATION_CLASS.SystemHandleInformation, ptr, length, out wantedLength);
                    if (result == NT_STATUS.STATUS_INFO_LENGTH_MISMATCH)
                    {
                        length = Math.Max(length, wantedLength);
                        Marshal.FreeHGlobal(ptr);
                        ptr = IntPtr.Zero;
                    }
                    else if (result == NT_STATUS.STATUS_SUCCESS)
                        break;
                    else
                        throw new Exception("Failed to retrieve system handle information.");
                }

                int handleCount = IntPtr.Size == 4 ? Marshal.ReadInt32(ptr) : (int) Marshal.ReadInt64(ptr);
                int offset = IntPtr.Size;
                int size = Marshal.SizeOf(typeof(SystemHandleEntry));
                for (int i = 0; i < handleCount; i++)
                {
                    var struc = (SystemHandleEntry) Marshal.PtrToStructure((IntPtr) ((int) ptr + offset), typeof(SystemHandleEntry));
                    yield return new HandleInfo(struc.OwnerProcessId, struc.Handle, struc.GrantedAccess, struc.ObjectTypeNumber);
                    offset += size;
                }
            }
            finally
            {
                if (ptr != IntPtr.Zero)
                    Marshal.FreeHGlobal(ptr);
            }
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct SystemHandleEntry
        {
            public int OwnerProcessId;
            public byte ObjectTypeNumber;
            public byte Flags;
            public ushort Handle;
            public IntPtr Object;
            public int GrantedAccess;
        }
    }

    enum NT_STATUS
    {
        STATUS_SUCCESS = 0x00000000,
        STATUS_BUFFER_OVERFLOW = unchecked((int) 0x80000005L),
        STATUS_INFO_LENGTH_MISMATCH = unchecked((int) 0xC0000004L)
    }

    enum SYSTEM_INFORMATION_CLASS
    {
        SystemBasicInformation = 0,
        SystemPerformanceInformation = 2,
        SystemTimeOfDayInformation = 3,
        SystemProcessInformation = 5,
        SystemProcessorPerformanceInformation = 8,
        SystemHandleInformation = 16,
        SystemInterruptInformation = 23,
        SystemExceptionInformation = 33,
        SystemRegistryQuotaInformation = 37,
        SystemLookasideInformation = 45
    }

    enum OBJECT_INFORMATION_CLASS
    {
        ObjectBasicInformation = 0,
        ObjectNameInformation = 1,
        ObjectTypeInformation = 2,
        ObjectAllTypesInformation = 3,
        ObjectHandleInformation = 4
    }

    static class NativeMethods
    {
        [DllImport("ntdll.dll")]
        internal static extern NT_STATUS NtQuerySystemInformation(
            [In] SYSTEM_INFORMATION_CLASS SystemInformationClass,
            [In] IntPtr SystemInformation,
            [In] int SystemInformationLength,
            [Out] out int ReturnLength);

        [DllImport("ntdll.dll")]
        internal static extern NT_STATUS NtQueryObject(
            [In] IntPtr Handle,
            [In] OBJECT_INFORMATION_CLASS ObjectInformationClass,
            [In] IntPtr ObjectInformation,
            [In] int ObjectInformationLength,
            [Out] out int ReturnLength);

        [DllImport("kernel32.dll")]
        internal static extern IntPtr GetCurrentProcess();

        [DllImport("kernel32.dll", SetLastError = true)]
        public static extern IntPtr OpenProcess(
            [In] int dwDesiredAccess,
            [In, MarshalAs(UnmanagedType.Bool)] bool bInheritHandle,
            [In] int dwProcessId);

        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        internal static extern bool CloseHandle(
            [In] IntPtr hObject);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool DuplicateHandle(
            [In] IntPtr hSourceProcessHandle,
            [In] IntPtr hSourceHandle,
            [In] IntPtr hTargetProcessHandle,
            [Out] out IntPtr lpTargetHandle,
            [In] int dwDesiredAccess,
            [In, MarshalAs(UnmanagedType.Bool)] bool bInheritHandle,
            [In] int dwOptions);
    }
}
Roman Starkov
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2

This is probably irrelevant and if it is please someone comment but there was a work-around I've used in explorer before to get around file locks.
If a file was locked by a process that had died Windows often wouldn't let you delete it but if you created a new file of the same name somewhere else, moved it to the folder it would succeed. You could then delete the new file and all was well.
To use this for your app you'd have to be able to read the file and hold it in memory before you did this then you write it back out after you'd got rid of the old one.
Maybe it will help, maybe not but it's worth trying.

Daniel
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2
    foreach (var process in Process.GetProcessesByName("excel")) //whatever you need to close 
    {
        if (process.MainWindowTitle.Contains("test.xlsx"))
        {
            process.Kill();
            break;
        }
    }

or

    foreach (var process in Process.GetProcesses())
    {
        if (process.MainWindowTitle.Contains("test.dat"))
        {
            process.Kill();
            break;
        }
    }
Lin
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2

Try Unlocker. If you try and delete the file that is locked by another process, it will list the process(es) that have the file locked. You can then unlock the file by shutting down those processes.

Peter Mortensen
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AndrewB
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  • oops did not notice that you wanted it progmaticly – AndrewB May 13 '09 at 23:05
  • this is a great app, i'm voting up your answer because of it. – aronchick May 14 '09 at 16:40
  • Process Explorer from Sysinternals can find also the process which are locking a file. Just use **Find**, **Find Handle or Dll** in the main menu. Enter the path of the file in the textbox, then click **Search**. – Maxence Apr 24 '15 at 08:38
1

I believe that you need code running in kernel mode to completely answer the question (but I haven't looked at the restart manager API).

You can enumerate all processes and their modules - so if the file you're looking for is a module (DLL, EXE, OCX...), you're good to go. But if it's a text file for example, you have to look at the kernel handle table which you cannot see from user mode. Handle.exe has a kernel driver in order to do that.

Remi Lemarchand
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0

I rewrote the GetProcessesLockingFile() method in the solution. The code was not working.

For example, you have a folder "C:\folder1\folder2" and a process in folder2 (process1). If the process was running, GetProcessesLockingFile() was returning "C:\folder1\folder2". So the condition if (files.Contains(filePath)) => if ("C:\folder1\folder2".contains("C:\folder1\folder2\process1")) was never true.

So this is my solution:

public static List<Process> GetProcessesLockingFile(FileInfo file)
{
    var procs = new List<Process>();

    var processListSnapshot = Process.GetProcesses();
    foreach (var process in processListSnapshot)
    {
        if (process.Id <= 4) { continue; } // system processes

        List<string> paths = GetFilesLockedBy(process);
        foreach (string path in paths)
        {
            string pathDirectory = path;
            if (!pathDirectory.EndsWith(Constants.DOUBLE_BACKSLASH))
            {
                pathDirectory = pathDirectory + Constants.DOUBLE_BACKSLASH;
            }
            string lastFolderName = Path.GetFileName(Path.GetDirectoryName(pathDirectory));

            if (file.FullName.Contains(lastFolderName))
            {
                procs.Add(process);
            }
        }
    }
    return procs;
}

Or with a string parameter:

public static List<Process> GetProcessesLockingFile(string filePath)
{
    var procs = new List<Process>();

    var processListSnapshot = Process.GetProcesses();
    foreach (var process in processListSnapshot)
    {
        if (process.Id <= 4) { continue; } // system processes

        List<string> paths = GetFilesLockedBy(process);
        foreach (string path in paths)
        {
            string pathDirectory = path;
            if (!pathDirectory.EndsWith(Constants.DOUBLE_BACKSLASH))
            {
                pathDirectory = pathDirectory + Constants.DOUBLE_BACKSLASH;
            }
            string lastFolderName = Path.GetFileName(Path.GetDirectoryName(pathDirectory));

            if (filePath.Contains(lastFolderName))
            {
                procs.Add(process);
            }
        }
    }
    return procs;
}
CarenRose
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0

Using dotnet core (net6) I solved this problem by using the win32 restart manager (as others have also mentioned). However some of the linked articles have elaborate code importing DLLs and calling those.

After finding an app to kill processes that lock a file written by meziantou. I found out that he publishes .Net wrappers for win32 dlls (including the restart manager).

Leveraging his work, I was able to fix this problem with the following code:

using Meziantou.Framework.Win32;

public static IEnumerable<Process> GetProcessesLockingFile(string filePath)
{
    using var session = RestartManager.CreateSession();
    session.RegisterFile(filePath);
    return session.GetProcessesLockingResources();
} 
Rob
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0

You absolutely don't need to run in Kernel mode (!!!)
It's a Win32 FAQ since Windows 95 (!) (in C, Google groups, Win32) : read the handle table, from User mode of course, and get the PID from the File handle ...

-1

simpler with linq:

public void KillProcessesAssociatedToFile(string file)
    {
        GetProcessesAssociatedToFile(file).ForEach(x =>
        {
            x.Kill();
            x.WaitForExit(10000);
        });
    }

    public List<Process> GetProcessesAssociatedToFile(string file)
    {
        return Process.GetProcesses()
            .Where(x => !x.HasExited
                && x.Modules.Cast<ProcessModule>().ToList()
                    .Exists(y => y.FileName.ToLowerInvariant() == file.ToLowerInvariant())
                ).ToList();
    }
Aalok
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