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How to check whether two file names point to the same physical file in C/C#/cmd on Windows? [duplicate]

Does anybody know how can get real path from symlink file or folder? Thank you!

Hello guys after my research I found this solution for how to get real path of a Symlink. If you have a created symlink and want to check where is the real pointer of this file or folder. If someone have better way to write it please share.
[DllImport("kernel32.dll", EntryPoint = "CreateFileW", CharSet = CharSet.Unicode, SetLastError = true)]
private static extern SafeFileHandle CreateFile(string lpFileName, int dwDesiredAccess, int dwShareMode, IntPtr securityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);
[DllImport("kernel32.dll", EntryPoint = "GetFinalPathNameByHandleW", CharSet = CharSet.Unicode, SetLastError = true)]
private static extern int GetFinalPathNameByHandle([In] SafeFileHandle hFile, [Out] StringBuilder lpszFilePath, [In] int cchFilePath, [In] int dwFlags);
private const int CREATION_DISPOSITION_OPEN_EXISTING = 3;
private const int FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
public static string GetRealPath(string path)
{
if (!Directory.Exists(path) && !File.Exists(path))
{
throw new IOException("Path not found");
}
SafeFileHandle directoryHandle = CreateFile(path, 0, 2, IntPtr.Zero, CREATION_DISPOSITION_OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, IntPtr.Zero); //Handle file / folder
if (directoryHandle.IsInvalid)
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
StringBuilder result = new StringBuilder(512);
int mResult = GetFinalPathNameByHandle(directoryHandle, result, result.Capacity, 0);
if (mResult < 0)
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
if (result.Length >= 4 && result[0] == '\\' && result[1] == '\\' && result[2] == '?' && result[3] == '\\')
{
return result.ToString().Substring(4); // "\\?\" remove
}
return result.ToString();
}

Binding static IP settings

I'm trying to configure a device's TCP/IP settings via registries but i can't seem to get it to work without a soft reboot.
I've been scouring Google for an answer and found that the way to do it is to pinvoke DeviceIoControl().
I've looked at the registries and they are definitely changing to the ones i want, I can't get DeviceIoControl() to return anything except 0 (fail) and I'm not sure what I'm doing wrong.
[DllImport("coredll.dll", EntryPoint = "CreateFile", SetLastError = true)]
private static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess, uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition, uint dwFLagsAndAttributes, IntPtr hTemplateFile);
[DllImport("coredll.dll", EntryPoint = "DeviceIoControl", SetLastError = true)]
private static extern int DeviceIoControl(IntPtr hDevice, uint dwIoControlCode, ref string lpInBuffer, int nInBufferSize, out string lpOutBuffer, int nOutBufferSize, ref int lpBytesReturned, IntPtr lpOverlapped);
[DllImport("coredll.dll", EntryPoint = "CloseHandle", SetLastError = true)]
private static extern bool CloseHandle(IntPtr hObject);
public static void SetTCPIP()
{
RegistryKey baseKey = Registry.LocalMachine;
string subKey = #"Comm\FEC1\Parms\TcpIp";
string enableDhcpKey = "EnableDHCP";
string gatewayKey = "DefaultGateway";
string ipAddressKey = "IpAddress";
string subnetMaskKey = "Subnetmask";
string ipAddress = "192.168.8.100";
string subnetMask = "255.255.255.0";
string gateway = "192.168.8.1";
WriteReg(baseKey, subKey, enableDhcpKey, 0);
WriteRegMultiString(baseKey, subKey, ipAddressKey, ipAddress);
WriteRegMultiString(baseKey, subKey, gatewayKey, gateway);
WriteRegMultiString(baseKey, subKey, subnetMaskKey, subnetMask);
CommitLocalMachineRegistry(); //RegFlushKey()
BindAdapter();
}
private static void BindAdapter()
{
const uint genericRead = 0x80000000;
const uint genericWrite = 0x40000000;
const int IOCTL_NDIS_REBIND_ADAPTER = 0x17002E;
const int OPEN_EXISTING = 3;
const string NI = #"NDS0:";
//Open the Handle to Rebind the Network Adapter
IntPtr hNdis = CreateFile(NI, genericRead | genericWrite, 0, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);
if (hNdis == IntPtr.Zero)
{
Debug.WriteLine("!!!!!!!!!!!!!!!!!"+hNdis);
}
string Adapter = "FEC1\0";
string OutBuffer = "";
int bytesReturned = 0;
//Rebind the Network Adapter
int check = DeviceIoControl(hNdis, IOCTL_NDIS_REBIND_ADAPTER, ref Adapter, Adapter.Length,
out OutBuffer, 0, ref bytesReturned, IntPtr.Zero);
if (check==0)
{
Debug.WriteLine("!!!!!!!!!!!!!!!!!!");
Debug.WriteLine(Marshal.GetLastWin32Error());
}
//Close the Handle
CloseHandle(hNdis);
}
I've tried getting more info on the issue using GetLastWin32Error() but it's returning 0 as well
Edit (couldn't add comment)
i've tried having Adapter = "FEC1\0\0" and I've also tried marshalling as a StringBuilder with no luck
Edit 2
Registries are HIVE based, so changes persist after a reboot.

How to launch detached process through cmd.exe with no console?

I want to launch an external program from C# to be completely detached.
I use CreateProcess through pinvoke because Process.Start doesn't allow me to use DETACHED_PROCESS. Also I want this application to redirect it's output to some file.
Here's the sample code:
var processInformation = new ProcessUtility.PROCESS_INFORMATION();
var securityInfo = new ProcessUtility.STARTUPINFO();
var sa = new ProcessUtility.SECURITY_ATTRIBUTES();
sa.Length = Marshal.SizeOf(sa);
// Create process with no window and totally detached
var result = ProcessUtility.CreateProcess(Path.Combine(Environment.SystemDirectory, "cmd.exe"), commandLineArguments, ref sa, ref sa, false,
ProcessUtility.DETACHED_PROCESS, IntPtr.Zero, null, ref securityInfo, out processInformation);
CommandLineArguments are something like this : "/c Foo.bat > Foo.log 2>&1"
Everything works fine and Foo.log is populated by Foo.bat. No additional console window is visible. PERFECT.
CommandLineArguments are something like this : "/c Foo.exe > Foo.log 2>&1"
Foo.exe is .NET Console Application.
Foo.log is not populated and Foo.exe is launched in visible console window. STRANGE. Why behavior is different from 1. ?
Just for your information. CommandLineArguments are something like this : "/c Foo.exe > Foo.log 2>&1"
Foo.exe is .NET Windows Application.
Everything works fine but when I launch this application simply from command prompt I see no output because no console is allocated.
I want 2. work the same as 1. Why there's a difference ?
UPDATE: I don't want to write the Foo.log for myself because launching application will be killed.
UPDATE: Ok, I wrote some code to specify that only one handle is inherited but CreateProcess gives me error 87 when calling with EXTENDED_STARTUPINFO_PRESENT ( even if it's present and empty ).
Can you please help me why?
public class ProcessUtility
{
// Process creation flags
const uint ZERO_FLAG = 0x00000000;
const uint CREATE_BREAKAWAY_FROM_JOB = 0x01000000;
const uint CREATE_DEFAULT_ERROR_MODE = 0x04000000;
const uint CREATE_NEW_CONSOLE = 0x00000010;
const uint CREATE_NEW_PROCESS_GROUP = 0x00000200;
const uint CREATE_NO_WINDOW = 0x08000000;
const uint CREATE_PROTECTED_PROCESS = 0x00040000;
const uint CREATE_PRESERVE_CODE_AUTHZ_LEVEL = 0x02000000;
const uint CREATE_SEPARATE_WOW_VDM = 0x00001000;
const uint CREATE_SHARED_WOW_VDM = 0x00001000;
const uint CREATE_SUSPENDED = 0x00000004;
const uint CREATE_UNICODE_ENVIRONMENT = 0x00000400;
const uint DEBUG_ONLY_THIS_PROCESS = 0x00000002;
const uint DEBUG_PROCESS = 0x00000001;
const uint DETACHED_PROCESS = 0x00000008;
const uint EXTENDED_STARTUPINFO_PRESENT = 0x00080000;
const uint INHERIT_PARENT_AFFINITY = 0x00010000;
// Thread attributes flags
const uint PROC_THREAD_ATTRIBUTE_HANDLE_LIST = 0x00020002;
const uint PROC_THREAD_ATTRIBUTE_PARENT_PROCESS = 0x00020000;
// File creation flags
const uint FILE_ACCESS_WRITE = 0x40000000;
// StartupInfo flags
const int STARTF_USESTDHANDLES = 0x00000100;
[StructLayout(LayoutKind.Sequential)]
struct STARTUPINFO
{
public Int32 cb;
public string lpReserved;
public string lpDesktop;
public string lpTitle;
public Int32 dwX;
public Int32 dwY;
public Int32 dwXSize;
public Int32 dwXCountChars;
public Int32 dwYCountChars;
public Int32 dwFillAttribute;
public Int32 dwFlags;
public Int16 wShowWindow;
public Int16 cbReserved2;
public IntPtr lpReserved2;
public IntPtr hStdInput;
public IntPtr hStdOutput;
public IntPtr hStdError;
}
[StructLayout(LayoutKind.Sequential)]
struct STARTUPINFOEX
{
public STARTUPINFO StartupInfo;
public IntPtr lpAttributeList;
};
[StructLayout(LayoutKind.Sequential)]
struct PROCESS_INFORMATION
{
public IntPtr hProcess;
public IntPtr hThread;
public Int32 dwProcessID;
public Int32 dwThreadID;
}
[StructLayout(LayoutKind.Sequential)]
struct SECURITY_ATTRIBUTES
{
public Int32 Length;
public IntPtr lpSecurityDescriptor;
public bool bInheritHandle;
}
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern bool CreateProcess(
string lpApplicationName,
string lpCommandLine,
ref SECURITY_ATTRIBUTES lpProcessAttributes,
ref SECURITY_ATTRIBUTES lpThreadAttributes,
bool bInheritHandles,
uint dwCreationFlags,
IntPtr lpEnvironment,
string lpCurrentDirectory,
[In] ref STARTUPINFO lpStartupInfo,
out PROCESS_INFORMATION lpProcessInformation);
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern bool CreateProcess(
string lpApplicationName,
string lpCommandLine,
ref SECURITY_ATTRIBUTES lpProcessAttributes,
ref SECURITY_ATTRIBUTES lpThreadAttributes,
bool bInheritHandles,
uint dwCreationFlags,
IntPtr lpEnvironment,
string lpCurrentDirectory,
[In] ref STARTUPINFOEX lpStartupInfo,
out PROCESS_INFORMATION lpProcessInformation);
[DllImport("kernel32.dll")]
public static extern uint GetLastError();
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool UpdateProcThreadAttribute(
IntPtr lpAttributeList, uint dwFlags, IntPtr Attribute, IntPtr lpValue,
IntPtr cbSize, IntPtr lpPreviousValue, IntPtr lpReturnSize);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool InitializeProcThreadAttributeList(
IntPtr lpAttributeList, int dwAttributeCount, int dwFlags, ref IntPtr lpSize);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool DeleteProcThreadAttributeList(IntPtr lpAttributeList);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool CloseHandle(IntPtr hObject);
[DllImport("kernel32.dll", SetLastError = true)]
static extern SafeFileHandle CreateFile(
string lpFileName,
uint fileAccess,
[MarshalAs(UnmanagedType.U4)] FileShare fileShare,
SECURITY_ATTRIBUTES securityAttributes,
[MarshalAs(UnmanagedType.U4)] FileMode creationDisposition,
uint dwFlagsAndAttributes,
IntPtr hTemplateFile);
public static bool CreateProcessWithStdHandlesRedirect(string lpApplicationName, string lpCommandLine, string logFilename)
{
var startupInfo = new STARTUPINFOEX();
startupInfo.StartupInfo.cb = Marshal.SizeOf(startupInfo);
try
{
var lpSize = IntPtr.Zero;
if (InitializeProcThreadAttributeList(IntPtr.Zero, 1, 0, ref lpSize) || lpSize == IntPtr.Zero)
return false;
startupInfo.lpAttributeList = Marshal.AllocHGlobal(lpSize);
// Here startupInfo.lpAttributeList is initialized to hold 1 value
if (!InitializeProcThreadAttributeList(startupInfo.lpAttributeList, 1, 0, ref lpSize))
return false;
var fileSecurityAttributes = new SECURITY_ATTRIBUTES();
fileSecurityAttributes.Length = Marshal.SizeOf(fileSecurityAttributes);
// Create inheritable file handle
fileSecurityAttributes.bInheritHandle = true;
// Open log file for writing
using (var handle = CreateFile(logFilename, FILE_ACCESS_WRITE, FileShare.ReadWrite,
fileSecurityAttributes, FileMode.Create, 0, IntPtr.Zero))
{
var fileHandle = handle.DangerousGetHandle();
// Add filehandle to proc thread attribute list
if (!UpdateProcThreadAttribute(startupInfo.lpAttributeList, 0, (IntPtr)PROC_THREAD_ATTRIBUTE_HANDLE_LIST, fileHandle,
(IntPtr)IntPtr.Size, IntPtr.Zero, IntPtr.Zero))
return false;
startupInfo.StartupInfo.hStdError = fileHandle;
startupInfo.StartupInfo.hStdOutput = fileHandle;
// startupInfo.StartupInfo.hStdInput = ?;
startupInfo.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
var processInformation = new PROCESS_INFORMATION();
var securityAttributes = new SECURITY_ATTRIBUTES();
securityAttributes.Length = Marshal.SizeOf(securityAttributes);
securityAttributes.bInheritHandle = true;
// Create process with no window and totally detached
return ProcessUtility.CreateProcess(lpApplicationName, lpCommandLine, ref securityAttributes, ref securityAttributes, true,
DETACHED_PROCESS | EXTENDED_STARTUPINFO_PRESENT, IntPtr.Zero, null, ref startupInfo, out processInformation);
}
}
finally
{
if (startupInfo.lpAttributeList != IntPtr.Zero)
{
DeleteProcThreadAttributeList(startupInfo.lpAttributeList);
Marshal.FreeHGlobal(startupInfo.lpAttributeList);
}
}
}
}

In case 1, the instance of cmd.exe that you're launching can run the batch file itself. No child process is created.
In case 2, the instance of cmd.exe that you're launching has to run the console application as a child process. It has no way of knowing that you wanted the application to not be given a console window, so when it calls CreateProcess it does not use the DETACHED_PROCESS flag, and Windows creates a new console as normal.
In case 3, the child process is not a console application, so Windows does not create a console for it even though DETACHED_PROCESS was not specified.
The usual solution is to open the foo.log file yourself, launch the console application directly (rather than via cmd.exe) and use the STARTUP_INFO structure to pass the log file handle as the standard output and standard error for the new process. Once CreateProcess has returned you can close the file handle. The duplicated handle in the child process will not be affected when your process closes.
However, I'm not sure how you would properly go about that in .NET. It's a bit tricky at the best of times, because you have to make the child process inherit the log file handle without having it inherit other handles inappropriately - that's probably the reason Process.Start is causing you problems. The recommended practice is to use a process/thread attribute list (InitializeProcThreadAttributeList) with a PROC_THREAD_ATTRIBUTE_HANDLE_LIST entry. (But the log handle still needs to be inheritable.)

Create a vb script, NoWindow.vbs, perhaps programmatically on the fly, as follows
CreateObject("Wscript.Shell").Run WScript.Arguments(0), 0, False
From you main app, call cscript simply with Process.Start
Process.Start("cscript", "NoWindow.vbs \"cmd /c Foo.exe > Foo.log 2>&1 \" ");
The vbs script itself will detach the process. No window is visible.
My testing was limited to using Procexp to confirm that the proceses Foo.exe was detached - Win7.

Chekout this answer to hide console:
How to Run a C# console application with the console hidden
And this answer to launch detached process :
Process Tree

Read a specific sector of DVD by Pinvoke in C#

I am reading directly from a disk using C# and pinvoking the kernel32 ReadFile method.i want just read a particular sector for save time but ReadFile read from first to N sector. How can read only own sector with my choice?
[StructLayout(LayoutKind.Sequential)]
public struct OVERLAPPED
{
public uint Internal;
public uint InternalHigh;
public uint Offset;
public uint OffsetHigh;
public int hEvent;
}
[DllImport("kernel32", SetLastError = true)]
static extern int CreateFile(string filename, uint desiredAccess, uint shareMode, IntPtr attributes, uint creationDisposition, uint flagsAndAttributes, IntPtr templateFile);
[DllImport("kernel32", SetLastError = true)]
public static extern Boolean CloseHandle(int handle);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern Boolean ReadFile(IntPtr hFile, Byte[] buffer, UInt32 BytesToRead, ref UInt32 BytedRead, OVERLAPPED OverLapped);
static int EIGHT_K = 8192;
static int FIVE_TWELVE_BYTES = 512;
static uint GENERIC_READ = 0x80000000;
static uint OPEN_EXISTING = 3;
static uint FILE_SHARE_READ = 1;
static uint FILE_SHARE_WRITE = 2;
[STAThread]
private void button1_Click(object sender, EventArgs e)
{
int fileHandle = 0;
bool returnVal = true;
try
{
// Open the device specified (Using the boot partition)
string deviceName = #"\\.\f:";
fileHandle = CreateFile(deviceName, GENERIC_READ,FILE_SHARE_READ | FILE_SHARE_WRITE, (IntPtr)0, OPEN_EXISTING, 0,(IntPtr)0);
if (fileHandle != -1)
{
Byte[] sector = new Byte[EIGHT_K];
UInt32 bytesRead = (uint)EIGHT_K;
OVERLAPPED ol = new OVERLAPPED();
// Can't get a FileStream ctor to work so I am using Win32 API ReadFile
bool worked = ReadFile((IntPtr)fileHandle, sector, (uint)EIGHT_K, ref bytesRead, ol);
return;
}
}
catch (Exception ex)
{
return;
}
finally
{
CloseHandle(fileHandle);
}
return;
}
I want to mark the DVD till required Original DVD to run the program.

Your OVERLAPPED struct is declared poorly and is incorrect in a 64 bit process. But in any case you don't need it. You are not performing overlapped I/O. Which is just as well because the declaration of ReadFile is incorrect. That function wants a pointer to an OVERLAPPED struct. You pass it by value.
In any case, you just don't need to consider overlapped I/O. So fix this issue by deleting the OVERLAPPED struct declaration from your code. And declare ReadFile like this:
[DllImport("kernel32.dll", SetLastError = true)]
public static extern Boolean ReadFile(IntPtr hFile, Byte[] buffer,
UInt32 BytesToRead, out UInt32 BytedRead, IntPtr Overlapped);
Pass IntPtr.Zero as the Overlapped parameter. And do make sure that you check the return value of ReadFile for an error.
The next step is to seek to a location in the file. Use SetFilePointerEx for that.
DllImport("kernel32.dll")]
static extern bool SetFilePointerEx(IntPtr hFile, long liDistanceToMove,
out long lpNewFilePointer, uint dwMoveMethod);
Consult the documentation for SetFilePointerEx to work out how to call this function.
Since you are using direct disk access, you will of course need to align the reads to sector boundaries.

Obtain a filename from a file handle?

I have the ntdll.dll's NtCreateFile() function hooked to allow/deny the access of certain files. Unlike kernel32.dll's CreateFile() which easily gives you the full path to the file in question, ntdll.dll's NtCreateFile() function only gives you the handle to the file. I need to obtain the full path of the file from a file handle, to consequently allow/deny access. I've searched around and there doesn't seem to be a working C# solution.
This solution is in C++, and documented from Microsoft. I've tried to port it over to C# with not much success. Here is my attempt at the C# equivalent of the C++ version of "obtaining a filename from a file handle":
public string GetFileNameFromHandle(IntPtr FileHandle)
{
string fileName = String.Empty;
IntPtr fileMap = IntPtr.Zero, fileSizeHi = IntPtr.Zero;
UInt32 fileSizeLo = 0;
fileSizeLo = GetFileSize(FileHandle, fileSizeHi);
if (fileSizeLo == 0 && fileSizeHi == IntPtr.Zero)
{
// cannot map an 0 byte file
return String.Empty;
}
fileMap = CreateFileMapping(FileHandle, IntPtr.Zero, FileMapProtection.PageReadonly, 0, 1, null);
if (fileMap != IntPtr.Zero)
{
IntPtr pMem = MapViewOfFile(fileMap, FileMapAccess.FileMapRead, 0, 0, 1);
if (pMem != IntPtr.Zero)
{
StringBuilder fn = new StringBuilder(250);
GetMappedFileName(System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle, pMem, fn, 250);
if (fileName.Length > 0)
{
UnmapViewOfFile(pMem);
CloseHandle(FileHandle);
return fn.ToString();
}
else
{
UnmapViewOfFile(pMem);
CloseHandle(FileHandle);
return String.Empty;
}
}
}
return String.Empty;
}
I have, of course, all the necessary DLLImports and user-defined types. When I use this function on handles, I get an empty string in return. It's also pretty hard to debug this, since this method is in a DLL that gets injected into a target process, not like something you can set a breakpoint at and enjoy Visual Studio's debugging system. I guess I could write a log file or some trace system, but I'm not that desperate yet. I just need a successful C# version of "get filename from file handle".
Any insight, code fixes, links?

Solved it myself. Here's the working code with the references and stuff.
[DllImport("kernel32.dll")]
static extern uint GetFileSize(IntPtr hFile, IntPtr lpFileSizeHigh);
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
public static extern IntPtr CreateFileMapping(
IntPtr hFile,
IntPtr lpFileMappingAttributes,
FileMapProtection flProtect,
uint dwMaximumSizeHigh,
uint dwMaximumSizeLow,
[MarshalAs(UnmanagedType.LPTStr)]string lpName);
[Flags]
public enum FileMapProtection : uint
{
PageReadonly = 0x02,
PageReadWrite = 0x04,
PageWriteCopy = 0x08,
PageExecuteRead = 0x20,
PageExecuteReadWrite = 0x40,
SectionCommit = 0x8000000,
SectionImage = 0x1000000,
SectionNoCache = 0x10000000,
SectionReserve = 0x4000000,
}
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr MapViewOfFile(
IntPtr hFileMappingObject,
FileMapAccess dwDesiredAccess,
uint dwFileOffsetHigh,
uint dwFileOffsetLow,
uint dwNumberOfBytesToMap);
[Flags]
public enum FileMapAccess : uint
{
FileMapCopy = 0x0001,
FileMapWrite = 0x0002,
FileMapRead = 0x0004,
FileMapAllAccess = 0x001f,
fileMapExecute = 0x0020,
}
[DllImport("psapi.dll", SetLastError = true)]
public static extern uint GetMappedFileName(IntPtr m_hProcess, IntPtr lpv, StringBuilder
lpFilename, uint nSize);
[DllImport("kernel32.dll", SetLastError = true)]
static extern bool UnmapViewOfFile(IntPtr lpBaseAddress);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool CloseHandle(IntPtr hObject);
public static string GetFileNameFromHandle(IntPtr FileHandle)
{
string fileName = String.Empty;
IntPtr fileMap = IntPtr.Zero, fileSizeHi = IntPtr.Zero;
UInt32 fileSizeLo = 0;
fileSizeLo = GetFileSize(FileHandle, fileSizeHi);
if (fileSizeLo == 0)
{
// cannot map an 0 byte file
return "Empty file.";
}
fileMap = CreateFileMapping(FileHandle, IntPtr.Zero, FileMapProtection.PageReadonly, 0, 1, null);
if (fileMap != IntPtr.Zero)
{
IntPtr pMem = MapViewOfFile(fileMap, FileMapAccess.FileMapRead, 0, 0, 1);
if (pMem != IntPtr.Zero)
{
StringBuilder fn = new StringBuilder(250);
GetMappedFileName(System.Diagnostics.Process.GetCurrentProcess().Handle, pMem, fn, 250);
if (fn.Length > 0)
{
UnmapViewOfFile(pMem);
CloseHandle(FileHandle);
return fn.ToString();
}
else
{
UnmapViewOfFile(pMem);
CloseHandle(FileHandle);
return "Empty filename.";
}
}
}
return "Empty filemap handle.";
}

From http://msdn.microsoft.com/en-us/library/aa366789.aspx
"The following example obtains a file name from a handle to a file object using a file mapping object. It uses the CreateFileMapping and MapViewOfFile functions to create the mapping. Next, it uses the GetMappedFileName function to obtain the file name."
Code looks legit to me, hope that helps.

The code you posted here has been copied from the MSDN.
It has several disadvantages: It requires a real file bigger than 0 Bytes to work. It does not work for files of 0 Bytes nor does it work for directories. (and I'm not even talking about network drives)
I have posted a perfectly working code here:
How to get name associated with open HANDLE