Process Locking file , i cant solve error.

[MarcusVB]

Trying to figure out why this code does not work.
I am on windows 10 and this code does exactly what i need, but it does not work that well for me, i keep getting error here at this code line

strObjectTypeName = Marshal.PtrToStringUni(ipTemp, objObjectType.Name.Length >> 1)

The error message

An unhandled exception of type 'System.AccessViolationException' occurred in mscorlib.dll

Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

Here is the full class

Imports System.Collections.Generic
Imports System.Runtime.InteropServices
Imports System.Diagnostics
Imports System.Text
Imports System.Threading

Namespace FileLockInfo
    Public Class FileLocked


        ''' <summary>
        ''' Return a list of processes that hold on the given file.
        ''' </summary>
        Public Shared Function GetProcessesLockingFile(filePath As String) As List(Of Process)
            Dim procs = New List(Of Process)()

            For Each process__1 In Process.GetProcesses()
                Dim files = GetFilesLockedBy(process__1)
                If files.Contains(filePath) Then
                    procs.Add(process__1)
                End If
            Next
            Return procs
        End Function

        ''' <summary>
        ''' Return a list of file locks held by the process.
        ''' </summary>
        Public Shared Function GetFilesLockedBy(process As Process) As List(Of String)
            Dim outp = New List(Of String)()

            Dim ts As ThreadStart = New ThreadStart(
                Sub()
                    Try
                        outp = UnsafeGetFilesLockedBy(process)
                    Catch
                    End Try
                End Sub
            )

            Try
                Dim t = New Thread(ts)
                t.IsBackground = True
                t.Start()
                t.Join()
                'If Not t.Join(250) Then
                '    Try
                '        t.Abort()
                '    Catch
                '    End Try
                'End If
            Catch
            End Try

            Return outp
        End Function

#Region "Inner Workings"
        Private Shared Function UnsafeGetFilesLockedBy(process As Process) As List(Of String)
            Try
                Dim [handles] = GetHandles(process)
                Dim files = New List(Of String)()

                For Each handle In [handles]
                    Dim file = GetFilePath(handle, process)
                    If file IsNot Nothing Then
                        files.Add(file)
                    End If
                Next

                Return files
            Catch
                Return New List(Of String)()
            End Try
        End Function

        Const CNST_SYSTEM_HANDLE_INFORMATION As Integer = 16
        Const STATUS_INFO_LENGTH_MISMATCH As UInteger = &HC0000004UI
        Private Shared Function GetFilePath(sYSTEM_HANDLE_INFORMATION As Win32API.SYSTEM_HANDLE_INFORMATION, process As Process) As String
            If sYSTEM_HANDLE_INFORMATION.GrantedAccess = &H12019F OrElse
                sYSTEM_HANDLE_INFORMATION.GrantedAccess = &H1A019F OrElse
                sYSTEM_HANDLE_INFORMATION.GrantedAccess = &H120189 OrElse
                sYSTEM_HANDLE_INFORMATION.GrantedAccess = &H100000 Then
                Return Nothing
            End If

            Dim m_ipProcessHwnd As IntPtr = Win32API.OpenProcess(Win32API.ProcessAccessFlags.All, False, process.Id)
            Dim ipHandle As IntPtr = IntPtr.Zero
            Dim objBasic = New Win32API.OBJECT_BASIC_INFORMATION()
            Dim ipBasic As IntPtr = IntPtr.Zero
            Dim objObjectType = New Win32API.OBJECT_TYPE_INFORMATION()
            Dim ipObjectType As IntPtr = IntPtr.Zero
            Dim objObjectName = New Win32API.OBJECT_NAME_INFORMATION()
            Dim ipObjectName As IntPtr = IntPtr.Zero
            Dim strObjectTypeName As String = ""
            Dim strObjectName As String = ""
            Dim nLength As Integer = 0
            Dim nReturn As Integer = 0
            Dim ipTemp As IntPtr = IntPtr.Zero

            If Not Win32API.DuplicateHandle(m_ipProcessHwnd, sYSTEM_HANDLE_INFORMATION.Handle, Win32API.GetCurrentProcess(), ipHandle, 0, False, _
             Win32API.DUPLICATE_SAME_ACCESS) Then
                Return Nothing
            End If

            ipBasic = Marshal.AllocHGlobal(Marshal.SizeOf(objBasic))
            Win32API.NtQueryObject(ipHandle, CInt(Win32API.ObjectInformationClass.ObjectBasicInformation), ipBasic, Marshal.SizeOf(objBasic), nLength)
            objBasic = DirectCast(Marshal.PtrToStructure(ipBasic, objBasic.[GetType]()), Win32API.OBJECT_BASIC_INFORMATION)
            Marshal.FreeHGlobal(ipBasic)

            ipObjectType = Marshal.AllocHGlobal(objBasic.TypeInformationLength)
            nLength = objBasic.TypeInformationLength
            While CUInt(InlineAssignHelper(nReturn, Win32API.NtQueryObject(ipHandle, CInt(Win32API.ObjectInformationClass.ObjectTypeInformation), ipObjectType, nLength, nLength))) = Win32API.STATUS_INFO_LENGTH_MISMATCH
                Marshal.FreeHGlobal(ipObjectType)
                ipObjectType = Marshal.AllocHGlobal(nLength)
            End While

            objObjectType = DirectCast(Marshal.PtrToStructure(ipObjectType, objObjectType.[GetType]()), Win32API.OBJECT_TYPE_INFORMATION)
            If Is64Bits() Then
                ipTemp = New IntPtr(Convert.ToInt64(objObjectType.Name.Buffer.ToString(), 10) >> 32)
            Else
                ipTemp = objObjectType.Name.Buffer
            End If

            strObjectTypeName = Marshal.PtrToStringUni(ipTemp, objObjectType.Name.Length >> 1)
            Marshal.FreeHGlobal(ipObjectType)
            If strObjectTypeName <> "File" Then
                Return Nothing
            End If

            'nLength = objBasic.NameInformationLength
            nLength = &H1000
            ipObjectName = Marshal.AllocHGlobal(nLength)
            While CUInt(InlineAssignHelper(nReturn, Win32API.NtQueryObject(ipHandle, CInt(Win32API.ObjectInformationClass.ObjectNameInformation), ipObjectName, nLength, nLength))) = Win32API.STATUS_INFO_LENGTH_MISMATCH
                Marshal.FreeHGlobal(ipObjectName)
                ipObjectName = Marshal.AllocHGlobal(nLength)
            End While
            objObjectName = DirectCast(Marshal.PtrToStructure(ipObjectName, objObjectName.[GetType]()), Win32API.OBJECT_NAME_INFORMATION)

            If Is64Bits() Then
                ipTemp = New IntPtr(Convert.ToInt64(objObjectName.Name.Buffer.ToString(), 10) >> 32)
            Else
                ipTemp = objObjectName.Name.Buffer
            End If

            If ipTemp <> IntPtr.Zero Then

                Dim baTemp As Byte() = New Byte(nLength - 1) {}
                Try
                    Marshal.Copy(ipTemp, baTemp, 0, nLength)

                    strObjectName = Marshal.PtrToStringUni(If(Is64Bits(), New IntPtr(ipTemp.ToInt64()), New IntPtr(ipTemp.ToInt32())))
                Catch generatedExceptionName As AccessViolationException
                    Return Nothing
                Finally
                    Marshal.FreeHGlobal(ipObjectName)
                    Win32API.CloseHandle(ipHandle)
                End Try
            End If

            Dim path As String = GetRegularFileNameFromDevice(strObjectName)
            Try
                Return path
            Catch
                Return Nothing
            End Try
        End Function

        Private Shared Function GetRegularFileNameFromDevice(strRawName As String) As String
            Dim strFileName As String = strRawName
            For Each strDrivePath As String In Environment.GetLogicalDrives()
                Dim sbTargetPath As New StringBuilder(Win32API.MAX_PATH)
                If Win32API.QueryDosDevice(strDrivePath.Substring(0, 2), sbTargetPath, Win32API.MAX_PATH) = 0 Then
                    Return strRawName
                End If
                Dim strTargetPath As String = sbTargetPath.ToString()
                If strFileName.StartsWith(strTargetPath) Then
                    strFileName = strFileName.Replace(strTargetPath, strDrivePath.Substring(0, 2))
                    Exit For
                End If
            Next
            Return strFileName
        End Function

        Private Shared Function GetHandles(process As Process) As List(Of Win32API.SYSTEM_HANDLE_INFORMATION)
            Dim nStatus As UInteger
            Dim nHandleInfoSize As Integer = &H10000
            Dim ipHandlePointer As IntPtr = Marshal.AllocHGlobal(nHandleInfoSize)
            Dim nLength As Integer = 0
            Dim ipHandle As IntPtr = IntPtr.Zero

            While (InlineAssignHelper(nStatus, Win32API.NtQuerySystemInformation(CNST_SYSTEM_HANDLE_INFORMATION, ipHandlePointer, nHandleInfoSize, nLength))) = STATUS_INFO_LENGTH_MISMATCH
                nHandleInfoSize = nLength
                Marshal.FreeHGlobal(ipHandlePointer)
                ipHandlePointer = Marshal.AllocHGlobal(nLength)
            End While

            Dim baTemp As Byte() = New Byte(nLength - 1) {}
            Marshal.Copy(ipHandlePointer, baTemp, 0, nLength)

            Dim lHandleCount As Long = 0
            If Is64Bits() Then
                lHandleCount = Marshal.ReadInt64(ipHandlePointer)
                ipHandle = New IntPtr(ipHandlePointer.ToInt64() + 8)
            Else
                lHandleCount = Marshal.ReadInt32(ipHandlePointer)
                ipHandle = New IntPtr(ipHandlePointer.ToInt32() + 4)
            End If

            Dim shHandle As Win32API.SYSTEM_HANDLE_INFORMATION
            Dim lstHandles As New List(Of Win32API.SYSTEM_HANDLE_INFORMATION)()

            For lIndex As Long = 0 To lHandleCount - 1
                shHandle = New Win32API.SYSTEM_HANDLE_INFORMATION()
                If Is64Bits() Then
                    shHandle = DirectCast(Marshal.PtrToStructure(ipHandle, shHandle.[GetType]()), Win32API.SYSTEM_HANDLE_INFORMATION)
                    ipHandle = New IntPtr(ipHandle.ToInt64() + Marshal.SizeOf(shHandle) + 8)
                Else
                    ipHandle = New IntPtr(ipHandle.ToInt64() + Marshal.SizeOf(shHandle))
                    shHandle = DirectCast(Marshal.PtrToStructure(ipHandle, shHandle.[GetType]()), Win32API.SYSTEM_HANDLE_INFORMATION)
                End If
                If shHandle.ProcessID <> process.Id Then
                    Continue For
                End If

                lstHandles.Add(shHandle)
            Next
            Return lstHandles

        End Function

        Private Shared Function Is64Bits() As Boolean
            Return If(Marshal.SizeOf(GetType(IntPtr)) = 8, True, False)
        End Function

        Friend Class Win32API
            <DllImport("ntdll.dll")> _
            Public Shared Function NtQueryObject(ObjectHandle As IntPtr, ObjectInformationClass As Integer, ObjectInformation As IntPtr, ObjectInformationLength As Integer, ByRef returnLength As Integer) As Integer
            End Function

            <DllImport("kernel32.dll", SetLastError:=True)> _
            Public Shared Function QueryDosDevice(lpDeviceName As String, lpTargetPath As StringBuilder, ucchMax As Integer) As UInteger
            End Function

            <DllImport("ntdll.dll")> _
            Public Shared Function NtQuerySystemInformation(SystemInformationClass As Integer, SystemInformation As IntPtr, SystemInformationLength As Integer, ByRef returnLength As Integer) As UInteger
            End Function

            <DllImport("kernel32.dll")> _
            Public Shared Function OpenProcess(dwDesiredAccess As ProcessAccessFlags, <MarshalAs(UnmanagedType.Bool)> bInheritHandle As Boolean, dwProcessId As Integer) As IntPtr
            End Function
            <DllImport("kernel32.dll")> _
            Public Shared Function CloseHandle(hObject As IntPtr) As Integer
            End Function
            <DllImport("kernel32.dll", SetLastError:=True)> _
            Public Shared Function DuplicateHandle(hSourceProcessHandle As IntPtr, hSourceHandle As UShort, hTargetProcessHandle As IntPtr, ByRef lpTargetHandle As IntPtr, dwDesiredAccess As UInteger, <MarshalAs(UnmanagedType.Bool)> bInheritHandle As Boolean, _
    dwOptions As UInteger) As <MarshalAs(UnmanagedType.Bool)> Boolean
            End Function
            <DllImport("kernel32.dll")> _
            Public Shared Function GetCurrentProcess() As IntPtr
            End Function

            Public Enum ObjectInformationClass As Integer
                ObjectBasicInformation = 0
                ObjectNameInformation = 1
                ObjectTypeInformation = 2
                ObjectAllTypesInformation = 3
                ObjectHandleInformation = 4
            End Enum

            <Flags()> _
            Public Enum ProcessAccessFlags As UInteger
                All = &H1F0FFF
                Terminate = &H1
                CreateThread = &H2
                VMOperation = &H8
                VMRead = &H10
                VMWrite = &H20
                DupHandle = &H40
                SetInformation = &H200
                QueryInformation = &H400
                Synchronize = &H100000
            End Enum

            <StructLayout(LayoutKind.Sequential)> _
            Public Structure OBJECT_BASIC_INFORMATION
                ' Information Class 0
                Public Attributes As Integer
                Public GrantedAccess As Integer
                Public HandleCount As Integer
                Public PointerCount As Integer
                Public PagedPoolUsage As Integer
                Public NonPagedPoolUsage As Integer
                Public Reserved1 As Integer
                Public Reserved2 As Integer
                Public Reserved3 As Integer
                Public NameInformationLength As Integer
                Public TypeInformationLength As Integer
                Public SecurityDescriptorLength As Integer
                Public CreateTime As System.Runtime.InteropServices.ComTypes.FILETIME
            End Structure

            <StructLayout(LayoutKind.Sequential)> _
            Public Structure OBJECT_TYPE_INFORMATION
                ' Information Class 2
                Public Name As UNICODE_STRING
                Public ObjectCount As Integer
                Public HandleCount As Integer
                Public Reserved1 As Integer
                Public Reserved2 As Integer
                Public Reserved3 As Integer
                Public Reserved4 As Integer
                Public PeakObjectCount As Integer
                Public PeakHandleCount As Integer
                Public Reserved5 As Integer
                Public Reserved6 As Integer
                Public Reserved7 As Integer
                Public Reserved8 As Integer
                Public InvalidAttributes As Integer
                Public GenericMapping As GENERIC_MAPPING
                Public ValidAccess As Integer
                Public Unknown As Byte
                Public MaintainHandleDatabase As Byte
                Public PoolType As Integer
                Public PagedPoolUsage As Integer
                Public NonPagedPoolUsage As Integer
            End Structure

            <StructLayout(LayoutKind.Sequential)> _
            Public Structure OBJECT_NAME_INFORMATION
                ' Information Class 1
                Public Name As UNICODE_STRING
            End Structure

            <StructLayout(LayoutKind.Sequential, Pack:=1)> _
            Public Structure UNICODE_STRING
                Public Length As UShort
                Public MaximumLength As UShort
                Public Buffer As IntPtr
            End Structure

            <StructLayout(LayoutKind.Sequential)> _
            Public Structure GENERIC_MAPPING
                Public GenericRead As Integer
                Public GenericWrite As Integer
                Public GenericExecute As Integer
                Public GenericAll As Integer
            End Structure

            <StructLayout(LayoutKind.Sequential, Pack:=1)> _
            Public Structure SYSTEM_HANDLE_INFORMATION
                ' Information Class 16
                Public ProcessID As Integer
                Public ObjectTypeNumber As Byte
                Public Flags As Byte
                ' 0x01 = PROTECT_FROM_CLOSE, 0x02 = INHERIT
                Public Handle As UShort
                Public Object_Pointer As Integer
                Public GrantedAccess As UInt32
            End Structure

            Public Const MAX_PATH As Integer = 260
            Public Const STATUS_INFO_LENGTH_MISMATCH As UInteger = &HC0000004UI
            Public Const DUPLICATE_SAME_ACCESS As Integer = &H2
        End Class
        Private Shared Function InlineAssignHelper(Of T)(ByRef target As T, value As T) As T
            target = value
            Return value
        End Function
#End Region
    End Class
End Namespace

And here is how i call it

    Private Sub Whoislockingf_Click(sender As Object, e As EventArgs) Handles Whoislockingf.Click
        For Each P As Process In FileLockInfo.FileLocked.GetProcessesLockingFile("F:\Testfile") 'Example place of file that is locked by anbother process
            ListBox1.Items.Add(P.ProcessName)
        Next
    End Sub

I think i just missing something easy. but i dont know where,
I compile it as 64 bit and have tried "Any CPU" but same results.


If anyone could try it out and maby figure this one out any help would be appreciated!

[Shaggy Hiker]

The threading you are using seems a bit off, but it also seems irrelevant to the question at hand.

If you were to strip out all the threading, and also strip out the loops such that you are calling a simpler method for just the first P in the collection, do you still get the error?

My thinking is that you are currently complicating the situation with the threading, which boils down to just this:

Dim files = New List(Of String)()

                For Each handle In [handles]
                    Dim file = GetFilePath(handle, process)
                    If file IsNot Nothing Then
                        files.Add(file)
                    End If
                Next

so it would be good to try that without the threading to ensure that you still get the error. I expect that you will, but it would be more interesting if you did not.

[MarcusVB]

Hey thanks for the input, i tried that and now the listbox seems to add something, but it stops and i still get that error after a few seconds of the listbox filling up, with what results i can not see.

[Shaggy Hiker]

So, the loop runs for a while...then stops? That's some interesting information. Not GOOD news, in my opinion, but interesting.

Had it failed on the first iteration, that would be relatively simple and straightforward to address. It sounds like that did not happen. The first iteration sounds like it worked fine.

One further test you might try is to add a GC.Collect statement such that you force garbage collection after each iteration of the loop. This is a horrible thing to do in real code, but as a test, it might be revealing. My thinking is that you appear to have a memory issue going on, based on the error message. You are also doing a fair amount of direct memory work, which is not generally done in .NET. I'm wondering whether or not that memory action (the alloc calls) is getting things into a confused state.

Of course, this test would be solely informational. After all, if GC.Collect caused the error to go away, that's not really a solution, because the cure would be pretty bad.

[MarcusVB]

Yes, it looks like it was wanting to work, but in the end failed, i tried skiping that error and apparently it seems it lists all processes in use by windows, that is not the solution i was going for though.
But i think i will have to put this one on ice for a while untill i have time to figure it out.

Thank you for trying to help!

[Niya]

Whats with all the Is64Bits calls? This is EXACTLY the point of the IntPtr type, so you don't have to do those checks. IntPtr will always be the correct size, no need to check if you're running 32 bit or 64 bit.