API: FindFirstFileW and FindNextFileW

[Howard Kaikow]

Without using the System.IO, etc, libraries, I'd like to find an example of how to use the Unicode API functions FindFirstFileW and FindNextFileW in VB .Net.

 

The goal is to convert the VB 6 code to VB .Net.

[Wile]

I havent looked at the vb code, but if you need to use API functions instead of .net methods to avoid a problem, a good starting point is http://www.pinvoke.net/index.aspx

This is a wiki containing most (if not all) of the windows API with definition (and often examples) to pinvoke them -> call them from .net. For FindFirstFile it finds: http://www.pinvoke.net/default.aspx/kernel32/FindFirstFile.html

 

Hope this helps.

[Howard Kaikow]

I havent looked at the vb code, but if you need to use API functions instead of .net methods to avoid a problem, a good starting point is http://www.pinvoke.net/index.aspx

This is a wiki containing most (if not all) of the windows API with definition (and often examples) to pinvoke them -> call them from .net. For FindFirstFile it finds: http://www.pinvoke.net/default.aspx/kernel32/FindFirstFile.html

 

Hope this helps.

 

THanx.

 

Looks like a useful site,

 

Is the following the Unicode version?

 

[DllImport("kernel32", CharSet=CharSet.Unicode)]

public static extern IntPtr FindFirstFile(string lpFileName, out WIN32_FIND_DATA lpFindFileData);

[Howard Kaikow]

THanx.

 

Looks like a useful site,

 

Is the following the Unicode version?

 

[DllImport("kernel32", CharSet=CharSet.Unicode)]

public static extern IntPtr FindFirstFile(string lpFileName, out WIN32_FIND_DATA lpFindFileData);

Ah, I see that it is the Unicode version!

[PlausiblyDamp]

Just out of curiosity is there a reason you don't want to switch to the .Net way of ding things (System.IO etc.)?

 

It would really allow you to simplify the existing code if you dropped the interop stuff.

[Howard Kaikow]

Just out of curiosity is there a reason you don't want to switch to the .Net way of ding things (System.IO etc.)?

 

It would really allow you to simplify the existing code if you dropped the interop stuff.

 

Yes, I'm testing something.

 

I've converted the code at pinvoke.net to VB .NET, but there's a problem because I do not know how to pass the parameters in the unicode version.

 

When I get to

        hSearch = FindFirstFileW(Path & "*", WFD)

 

I get "Additional information: Object reference not set to an instance of an object.".

 

Do not know which object is being referenced.

 

 

Option Explicit On 
Option Strict On
Option Compare Text
Imports System.Runtime.InteropServices
'Imports Microsoft.VisualBasic.ControlChars
Imports System.IO
Public Class Form1
   Inherits System.Windows.Forms.Form

   <DllImport("kernel32", CharSet:=CharSet.Unicode, SetLastError:=False)> _
   Private Shared Function FindClose _
       (ByVal hFindFile As Integer) As Integer
   End Function

   <DllImport("kernel32", CharSet:=CharSet.Unicode, SetLastError:=True)> _
   Private Shared Function FindFirstFileW _
       (ByVal lpFileName As String, ByVal lpFindFileData As WIN32_FIND_DATA) As Integer
   End Function

   <DllImport("kernel32", CharSet:=CharSet.Unicode, SetLastError:=True)> _
   Private Shared Function FindNextFileW _
       (ByVal hFindFile As Integer, ByVal lpFindFileData As WIN32_FIND_DATA) As Integer
   End Function

   <DllImport("user32", CharSet:=CharSet.Unicode, SetLastError:=False)> _
   Private Shared Function SendMessage _
       (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByRef lParam As Integer) As Integer
   End Function

   Private Structure FILETIME
       Dim dwLowDateTime As Integer
       Dim dwHighDateTime As Integer
   End Structure

   Private Const ALTERNATE As Integer = 14
   Private Const FILE_ATTRIBUTE_DIRECTORY As Integer = &H10S
   Private Const INVALID_HANDLE_VALUE As Integer = -1
   Private Const MAX_PATH As Integer = 260
   Private Const LB_GETCOUNT As Integer = &H18BS
   Private Const LB_SETHORIZONTALEXTENT As Short = &H194S
   Private Const LB_SETTOPINDEX As Integer = &H197S

   <Serializable(), StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)> _
   Private Structure WIN32_FIND_DATA
       Dim dwFileAttributes As FileAttributes
       Dim ftCreationTime As FILETIME
       Dim ftLastAccessTime As FILETIME
       Dim ftLastWriteTime As FILETIME
       Dim nFileSizeHigh As Integer
       Dim nFileSizeLow As Integer
       Dim dwReserved0 As Integer
       Dim dwReserved1 As Integer
       <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=MAX_PATH)> _
         Dim cFileName As String
       <MarshalAs(UnmanagedType.ByValTStr, SizeConst:=ALTERNATE)> _
           Dim cAlternate As String
   End Structure

   Private Sub frmFindFirstFile_Activated(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles MyBase.Activated
       'With lstStuff
       '    'UPGRADE_ISSUE: Constant vbPixels was not upgraded. Click for more: 'ms-help://MS.VSCC.2003/commoner/redir/redirect.htm?keyword="vbup2070"'
       '    'UPGRADE_ISSUE: Constant vbTwips was not upgraded. Click for more: 'ms-help://MS.VSCC.2003/commoner/redir/redirect.htm?keyword="vbup2070"'
       '    'UPGRADE_ISSUE: Form method frmWFDTest.ScaleX was not upgraded. Click for more: 'ms-help://MS.VSCC.2003/commoner/redir/redirect.htm?keyword="vbup2064"'
       '    SendMessage(.Handle.ToInt32, LB_SETHORIZONTALEXTENT, ScaleX(VB6.PixelsToTwipsX(.Width), vbTwips, vbPixels) + 5000, 0)
       'End With
   End Sub

   Private Sub btnRunMe_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnRunMe.Click
       Dim lngCount As Integer
       Dim sFileName As String
       sFileName = txtDriveLetter.Text & ":\" ' Can be up to 32,767 chars
       lstStuff.Items.Clear()
       lngCount = 0
       FindMyFiles(sFileName, lngCount)
   End Sub
   Private Sub FindMyFiles(ByRef Path As String, ByRef lngFileCount As Integer)
       Dim k As Integer
       Dim NumberDirectories As Integer
       Dim strListDirectoryNames() As String
       ' The following can be Static or Private
       Dim Filename As String
       Dim hSearch As Integer
       Dim WFD As WIN32_FIND_DATA

       NumberDirectories = -1
       'hSearch = FindFirstFileW(StrPtr(Path & "*"), VarPtr(WFD))
       hSearch = FindFirstFileW(Path & "*", WFD)
       If hSearch <> INVALID_HANDLE_VALUE Then
           With txtProcessed
               Do
                   System.Windows.Forms.Application.DoEvents()
                   Filename = RemoveNulls(WFD.cFileName)
                   If (Filename <> ".") And (Filename <> "..") Then
                       If (WFD.dwFileAttributes And FILE_ATTRIBUTE_DIRECTORY) = 0 Then
                           lngFileCount = lngFileCount + 1
                           .Text = FormatNumber(lngFileCount, 0, , , TriState.True)
                           '                        With lstStuff
                           '                            .AddItem lngFileCount & ": " & Path & Filename
                           '                            k = SendMessage(.hwnd, LB_GETCOUNT, ByVal 0&, ByVal 0&)
                           '                            SendMessage .hwnd, LB_SETTOPINDEX, k - 1, ByVal 0&
                           '                        End With
                       Else
                           NumberDirectories = NumberDirectories + 1
                           ReDim Preserve strListDirectoryNames(NumberDirectories)
                           strListDirectoryNames(NumberDirectories) = Filename
                       End If
                   End If
                   'Loop While FindNextFileW(hSearch, VarPtr(WFD)) <> 0
               Loop While FindNextFileW(hSearch, WFD) <> 0
           End With
           k = FindClose(hSearch)
       End If

       If NumberDirectories <> -1 Then
           For k = 0 To NumberDirectories
               FindMyFiles(Path & strListDirectoryNames(k) & "\", lngFileCount)
           Next k
       End If
   End Sub

   Private Function RemoveNulls(ByRef OriginalString As String) As String
       Dim pos As Integer
       pos = InStr(OriginalString, Chr(0))
       If pos > 1 Then
           RemoveNulls = Mid(OriginalString, 1, pos - 1)
       Else
           RemoveNulls = OriginalString
       End If
   End Function
End Class

[Howard Kaikow]

Using FindFirstFileW, how does one convert the following to VB .NET, given the structures below, where Path is type String?

 

hSearch = FindFirstFileW(StrPtr(Path & "*"), VarPtr(WFD))

 

 

 

Dim WFD As WIN32_FIND_DATA

<DllImport("kernel32", CharSet:=CharSet.Unicode, SetLastError:=True)> _
Private Shared Function FindFirstFileW _
(ByVal lpFileName As String, ByVal lpFindFileData As WIN32_FIND_DATA) As
Integer
End Function

Private Structure FILETIME
Dim dwLowDateTime As Integer
Dim dwHighDateTime As Integer
End Structure

Private Const ALTERNATE As Integer = 14
Private Const MAX_PATH As Integer = 260

<Serializable(), StructLayout(LayoutKind.Sequential,
CharSet:=CharSet.Unicode)> _
Private Structure WIN32_FIND_DATA
Dim dwFileAttributes As FileAttributes
Dim ftCreationTime As FILETIME
Dim ftLastAccessTime As FILETIME
Dim ftLastWriteTime As FILETIME
Dim nFileSizeHigh As Integer
Dim nFileSizeLow As Integer
Dim dwReserved0 As Integer
Dim dwReserved1 As Integer
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=MAX_PATH)> _
Dim cFileName As String
<MarshalAs(UnmanagedType.ByValTStr, SizeConst:=ALTERNATE)> _
Dim cAlternate As String
End Structure

[PlausiblyDamp]

Try

    _
   Private Shared Function FindFirstFileW _
       (ByVal lpFileName As String, ByRef lpFindFileData As WIN32_FIND_DATA) As Integer
   End Function

for the declaration

 

and you should be able to call it like

hSearch = FindFirstFileW(Path & "*", WFD)

[Howard Kaikow]

Thanx.

 

I should have caught that.