How do I find out which process is locking a file using NET

Question

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  How does one figure out what process locked a file using c   Command line tool Across a Network Locking a USB device Unit test fails with locked file deleting locked file

User · Answer

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();
}

User · Answer

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  lt   processes GetUpperBound 0  - 1  i                          myProcess   processes i                 if   myProcess HasExited    This will cause an  Access is denied  error             if  myProcess Threads Count  gt  0                                try                                       ProcessModuleCollection modules   myProcess Modules                      int j   0                      for  j   0  j  lt   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      amp  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  quot mscor  quot

User · Answer

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

User · Answer

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  lt   processes GetUpperBound 0  - 1  i               myProcess   processes i            if   myProcess HasExited                 try                    ProcessModuleCollection modules   myProcess Modules                   int j   0                   for  j   0  j  lt   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      amp  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      amp  exception Message               End Try         End If     Next i     Return myProcessArray End Function End Module

User · Answer

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();
}

User · Answer

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

User · Answer

simpler with linq   public void KillProcessesAssociatedToFile string file                GetProcessesAssociatedToFile file  ForEach x   gt                        x Kill                x WaitForExit 10000                          public List lt Process gt  GetProcessesAssociatedToFile string file                return Process GetProcesses                Where x   gt   x HasExited                  amp  amp  x Modules Cast lt ProcessModule gt    ToList                        Exists y   gt  y FileName ToLowerInvariant      file ToLowerInvariant                      ToList

User · Answer

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 lt Process gt  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             lt summary gt          Find out what process es  have a lock on the specified file           lt  summary gt           lt param name  path  gt Path of the file  lt  param gt           lt returns gt Processes locking the file lt  returns gt           lt remarks gt 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                    lt  remarks gt      static public List lt Process gt  WhoIsLocking string path                uint handle          string key   Guid NewGuid   ToString            List lt Process gt  processes   new List lt Process gt              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 lt Process gt   int pnProcInfo                           Enumerate all of the results and add them to the                         list to be returned                     for  int i   0  i  lt  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

User · Answer

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

User · Answer

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  lt   processes GetUpperBound 0  - 1  i               myProcess   processes i            if   myProcess HasExited                 try                    ProcessModuleCollection modules   myProcess Modules                   int j   0                   for  j   0  j  lt   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      amp  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      amp  exception Message               End Try         End If     Next i     Return myProcessArray End Function End Module

User · Answer

simpler with linq   public void KillProcessesAssociatedToFile string file                GetProcessesAssociatedToFile file  ForEach x   gt                        x Kill                x WaitForExit 10000                          public List lt Process gt  GetProcessesAssociatedToFile string file                return Process GetProcesses                Where x   gt   x HasExited                  amp  amp  x Modules Cast lt ProcessModule gt    ToList                        Exists y   gt  y FileName ToLowerInvariant      file ToLowerInvariant                      ToList

User · Answer

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  lt   processes GetUpperBound 0  - 1  i               myProcess   processes i            if   myProcess HasExited                 try                    ProcessModuleCollection modules   myProcess Modules                   int j   0                   for  j   0  j  lt   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      amp  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      amp  exception Message               End Try         End If     Next i     Return myProcessArray End Function End Module

User · Answer

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  lt   processes GetUpperBound 0  - 1  i                          myProcess   processes i                 if   myProcess HasExited    This will cause an  Access is denied  error             if  myProcess Threads Count  gt  0                                try                                       ProcessModuleCollection modules   myProcess Modules                      int j   0                      for  j   0  j  lt   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      amp  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  quot mscor  quot

User · Answer

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

User · Answer

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  lt   processes GetUpperBound 0  - 1  i               myProcess   processes i            if   myProcess HasExited                 try                    ProcessModuleCollection modules   myProcess Modules                   int j   0                   for  j   0  j  lt   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      amp  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      amp  exception Message               End Try         End If     Next i     Return myProcessArray End Function End Module

User · Answer

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 lt Process gt  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             lt summary gt          Find out what process es  have a lock on the specified file           lt  summary gt           lt param name  path  gt Path of the file  lt  param gt           lt returns gt Processes locking the file lt  returns gt           lt remarks gt 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                    lt  remarks gt      static public List lt Process gt  WhoIsLocking string path                uint handle          string key   Guid NewGuid   ToString            List lt Process gt  processes   new List lt Process gt              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 lt Process gt   int pnProcInfo                           Enumerate all of the results and add them to the                         list to be returned                     for  int i   0  i  lt  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

[c#] How do I find out which process is locking a file using .NET?

Examples related to c#

Examples related to file-locking