Q168519: PRB: Search Using OpenFile API Instead of Dir/Dir$ Function

Article: Q168519
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:4.0,5.0,6.0
Operating System(s): 
Keyword(s): kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
Last Modified: 11-JAN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Standard Edition for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition for Windows, version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The Dir/Dir$ function in Microsoft Visual Basic may be used to test for a file's
existence. It returns the name (or names) of the files that fit the search
criteria. However, when using a UNC (Universal Naming Conventions) path to
search for files that exist on a network directory, the Dir$ function may not
return valid information. This behavior is most common when searching network
paths. It can also occur when searching for files that have unusual names (such
as files that have no extension).

RESOLUTION
==========

To work around this behavior, the OpenFile API call may be used to test for the
existence of a file. Passing the parameter OF_EXIST to the OpenFile function
causes OpenFile to search for an existing file. It does not write to or open the
file when this parameter is passing by itself.

MORE INFORMATION
================

The following sample shows how to use the OpenFile API function to check for the
existence of a file named "Test" that has no file extension and is located at
the following location: \\ServerName\ShareName:

     'If using a 32-bit version of Visual Basic, this declaration is
     'required;

     Declare Function OpenFile Lib "kernel32" (ByVal lpFileName As String, _
                                               lpReOpenBuff As OFSTRUCT, _
                                               ByVal wStyle As Long) As Long

     'If using the 16-bit version of Visual Basic 4.0, this declaration is
     'required;

     Declare Function OpenFile Lib "kernel" (ByVal lpFileName As String, _
                                             lpReOpenBuff As OFSTRUCT, _
                                             ByVal wStyle As Integer) _
                                             As Integer

     'Both 16-bit and 32-bit utilize these constants and structure:

     Public Const OFS_MAXPATHNAME = 128
     Public Const OF_EXIST = &H4000

     Type OFSTRUCT
         cBytes As Byte
         fFixedDisk As Byte
         nErrCode As Integer
         Reserved1 As Integer
         Reserved2 As Integer
         szPathName(OFS_MAXPATHNAME) As Byte
     End Type

     'On the VB IDE menu bar select Tools/Options/Project/Startup Form and
     'set Sub Main() as the project start-up form.

     Sub main()
         Dim result As Integer
         Dim strPath As String
         Dim strucFname As OFSTRUCT
         Dim strResults As String
         Dim strSearchFile As String

         strSearchFile = "\\ServerName\ShareName\Test"

         result = OpenFile(strSearchFile, strucFname, OF_EXIST)

         'The above line causes OpenFile to search for the
         'file Test (no extension) on the server network path.
         'Passing the OF_EXIST parameter tells the OpenFile
         'function to search for the file, the file will not be
         'opened or modified in any way.

         If result <> -1 Then
             MsgBox "File found"
         Else
             MsgBox "File not found"
         End If
     End Sub

If the file in question is found, data pertaining to that file is placed into the
variable strucFname.

REFERENCES
==========

For additional information, please see the following article in the Microsoft
Knowledge Base:

  Q112674 : How to Determine If a File Exists by Using DIR$

Additional query words:

======================================================================
Keywords          : kbAPI kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Version           : WINDOWS:4.0,5.0,6.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.