How can I determine that several file paths formats point to the same physical location [duplicate]

Question

Possible Duplicate:
Best way to determine if two path reference to same file in C#

There are several ways to specify a directory location.

For example:
\\machineName\c$\rootPath\subPath
\\machineName\shareName (share pointing to subPath)
C:\rootPath\subPath
subPath (relative path if already in C:\rootPath

I need to determine that all of these paths "equal" each other (are really the same physical location on the hard drive).

Is there any way I can do this in C#?

Answer 1

As Oded states this is tricky to do in .Net. You could possibly cheat (depening on your exact requirements and permissions etc) by writing a file with a long randomly generated filename to the location and then seeing if you can see it from the other location. Bit of a hack but this is a pretty sound test I think, rather than relying on resolving mapped drives etc etc.

Ok many apologies for the VB - it's all I've got on this tiny netbook... C# wouldn't be too different...

usage eg

If sameLocation("\\machineName\c$\rootPath\subPath","\\machineName\shareName") Then...

Public Function sameLocation(ByVal sPath1 As String, ByVal sPath2 As String) As TriState
    Dim sFile As String = randomFilename()
    Dim sFullPath1 As String = sPath1 & "\" & sFile
    Dim sFullPath2 As String = sPath2 & "\" & sFile
    Dim bReturn As Boolean = False
    Try
        Dim fs As New FileStream(sFullPath1, FileMode.CreateNew)
        fs.Close()
    Catch ex As Exception
        Return TriState.UseDefault
    End Try

    Try
        bReturn = File.Exists(sFullPath2)
    Catch ex As Exception
        Return TriState.UseDefault
    End Try

    File.Delete(sFullPath1)
    Return bReturn
End Function

Public Function randomFilename() As String
    Dim r As New Random
    Randomize(My.Computer.Clock.TickCount)
    Dim sb As New StringBuilder
    Dim chars As Int16 = 100
    While chars > 0
        chars -= 1
        sb.Append(Chr(r.Next(26) + 65))
    End While
    Return sb.ToString
End Function

You could add more security, ie reading the timestamp etc...

Answer 2

You need to use GetFileInformationByHandle.
Check out this answer in StackOverflow and MSDN help.

Here is a method I wrote that works with directories:

using System;
using System.Runtime.InteropServices;

namespace CompareByPath    
{    
  public static class DirectoryHelper  
  {
    // all user defined types copied from 
    // http://pinvoke.net/default.aspx/kernel32.CreateFile
    // http://pinvoke.net/default.aspx/kernel32.GetFileInformationByHandle
    // http://pinvoke.net/default.aspx/kernel32.CloseHandle

    public const short INVALID_HANDLE_VALUE = -1;

    struct BY_HANDLE_FILE_INFORMATION
    {
      public uint FileAttributes;
      public System.Runtime.InteropServices.ComTypes.FILETIME CreationTime;
      public System.Runtime.InteropServices.ComTypes.FILETIME LastAccessTime;
      public System.Runtime.InteropServices.ComTypes.FILETIME LastWriteTime;
      public uint VolumeSerialNumber;
      public uint FileSizeHigh;
      public uint FileSizeLow;
      public uint NumberOfLinks;
      public uint FileIndexHigh;
      public uint FileIndexLow;
    }

    [Flags]
    public enum EFileAccess : uint
    {
      GenericRead = 0x80000000,
      GenericWrite = 0x40000000,
      GenericExecute = 0x20000000,
      GenericAll = 0x10000000
    }

    [Flags]
    public enum EFileShare : uint
    {
      None = 0x00000000,
      Read = 0x00000001,
      Write = 0x00000002,
      Delete = 0x00000004
    }

    [Flags]
    public enum EFileAttributes : uint
    {
      Readonly = 0x00000001,
      Hidden = 0x00000002,
      System = 0x00000004,
      Directory = 0x00000010,
      Archive = 0x00000020,
      Device = 0x00000040,
      Normal = 0x00000080,
      Temporary = 0x00000100,
      SparseFile = 0x00000200,
      ReparsePoint = 0x00000400,
      Compressed = 0x00000800,
      Offline = 0x00001000,
      NotContentIndexed = 0x00002000,
      Encrypted = 0x00004000,
      Write_Through = 0x80000000,
      Overlapped = 0x40000000,
      NoBuffering = 0x20000000,
      RandomAccess = 0x10000000,
      SequentialScan = 0x08000000,
      DeleteOnClose = 0x04000000,
      BackupSemantics = 0x02000000,
      PosixSemantics = 0x01000000,
      OpenReparsePoint = 0x00200000,
      OpenNoRecall = 0x00100000,
      FirstPipeInstance = 0x00080000
    }

    public enum ECreationDisposition : uint
    {
      New = 1,
      CreateAlways = 2,
      OpenExisting = 3,
      OpenAlways = 4,
      TruncateExisting = 5
    }

    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool GetFileInformationByHandle(IntPtr hFile, out        BY_HANDLE_FILE_INFORMATION lpFileInformation);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall, SetLastError = true)]
    static extern IntPtr CreateFile(String lpFileName, UInt32 dwDesiredAccess, UInt32 dwShareMode, IntPtr lpSecurityAttributes, UInt32 dwCreationDisposition, UInt32 dwFlagsAndAttributes, IntPtr hTemplateFile);

    [DllImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    static extern bool CloseHandle(IntPtr hObject);

    public static bool CompareDirectories(string d1, string d2)
    {
      bool result = false;

      BY_HANDLE_FILE_INFORMATION info1;
      BY_HANDLE_FILE_INFORMATION info2;

      IntPtr fileHandle1 = CreateFile(d1, (uint)EFileAccess.GenericRead, (uint)EFileShare.Read, IntPtr.Zero, (uint)ECreationDisposition.OpenExisting, (uint)(EFileAttributes.Directory | EFileAttributes.BackupSemantics), IntPtr.Zero);
      if (fileHandle1.ToInt32() != INVALID_HANDLE_VALUE)
      {
        bool rc = GetFileInformationByHandle(fileHandle1, out info1);
        if ( rc )
        {
          IntPtr fileHandle2 = CreateFile(d2, (uint)EFileAccess.GenericRead, (uint)EFileShare.Read, IntPtr.Zero, (uint)ECreationDisposition.OpenExisting, (uint)(EFileAttributes.Directory | EFileAttributes.BackupSemantics), IntPtr.Zero);
          if (fileHandle2.ToInt32() != INVALID_HANDLE_VALUE)
          {
            rc = GetFileInformationByHandle(fileHandle2, out info2);
            if ( rc )
            {
              if (( info1.FileIndexHigh == info2.FileIndexHigh) &&
                  ( info1.FileIndexLow == info2.FileIndexLow) &&
                  ( info1.VolumeSerialNumber == info2.VolumeSerialNumber))
              {
                result = true;
              }
            }
          }

          CloseHandle(fileHandle2);
        }
      }

      CloseHandle(fileHandle1);

      return result;
    }
  }
}