API FindFirstFile\F indNextFile vs GetFiles

[Lance]

Hi All,

I'm working on a program that requires searching multiple drives for multiple file types
and cataloging them based on certain geospatial attributes. All together, there are
hundreds of thousands of files on the drives. As part of the process, I'm currently using
the GetFiles method of the FileSystem object to retrieve collection of strings
representing a collection of a particular file type (for example, tif files). The problem
is that the GetFiles method doesn't seem to make any callbacks that would allow for me to
show some sort of meaningful progress, and the process can take a very long time. I know
I could fudge it with a marquee style progress bar and\or a busy mouse icon, but this
isn't ideal.

So, I was looking into using the API to do the grunt work. This would allow me to at
least display each filename in a label control as the search is being performed. I'm
trying to port Randy Birch's VB6 code available on his website at
http://vbnet.mvps.org/code/fileapi/r...l_multiple.htm . It's working
somewhat, except for the FindNextFile function which I've declared like so:

/////
Private Declare Function FindNextFile Lib "kernel32" _
Alias "FindNextFi leA" _
(ByVal hFindFile As Int32, _
ByVal lpFindFileData As WIN32_FIND_DATA ) As IntPtr
/////

As currently implemented, the function is not moving the search to the next file. It is
always returning the first file in the directory and it returns all the properties of that
file correctly. And it returns this first file for as many times as there are files in
the directory. I'm thinking it's because the WIN32_FIND_DATA - which is a UDT in the VB6
code - is defined as an object in my code and Dim'd as

/////
Dim WFD As WIN32_FIND_DATA = New WIN32_FIND_DATA
/////

at the beginning of the SearchForFiles Sub. For reference, in my code WIN32_FIND_DATA
defined like so:

/////
<StructLayout(L ayoutKind.Seque ntial, _
CharSet:=CharSe t.Auto)_
Friend Class WIN32_FIND_DATA
Friend sfileAttributes As Int32 = 0
Friend creationTime_lo wDateTime As Int32 = 0
Friend creationTime_hi ghDateTime As Int32 = 0
Friend lastAccessTime_ lowDateTime As Int32 = 0
Friend lastAccessTime_ highDateTime As Int32 = 0
Friend lastWriteTime_l owDateTime As Int32 = 0
Friend lastWriteTime_h ighDateTime As Int32 = 0
Friend nFileSizeHigh As Int32 = 0
Friend nFileSizeLow As Int32 = 0
Friend dwReserved0 As Int32 = 0
Friend dwReserved1 As Int32 = 0
<MarshalAs(Unma nagedType.ByVal TStr, SizeConst:=MAX_ PATH)_
Friend fileName As String = Nothing
<MarshalAs(Unma nagedType.ByVal TStr, SizeConst:=14)_
Friend alternateFileNa me As String = Nothing
End Class
/////

How can I make it so the FindNextFile call actually moves on to the next file in the
directory?

Lance

[Tom Shelton]

Lance wrote:

Thanks Tom. Remember, WIN32_FIND_DATA as a class caused the "FatalExecution EngineError "
using your declarations, but as a structure, it was running (although the output of the
members didn't seem to jive).

Private Const MAX_PATH As Integer = 260

' if you using vb2005, you can acually use
System.Runtim.I nteropServices. ComTypes.FILETI ME
<StructLayout(L ayoutKind.Seque ntial)_
Private Structure FILETIME
Public dwLowDateTime As Integer
Public dwHighDateTime As Integer
End Structure

<StructLayout(L ayoutKind.Seque ntial, CharSet:=CharSe t.Auto)_
Private Structure WIN32_FIND_DATA
Public dwFileAttribute s As Integer
Public ftCreationTime As FILETIME
Public ftLastAccessTim e As FILETIME
Public ftLastWriteTime As FILETIME
Public nFileSizeHigh As Integer
Public nFileSizeLow As Integer
Public dwReserved0 As Integer
Public dwReserved1 As Integer

<MarshalAs(Unma nagedType.ByVal TStr, SizeConst:=MAX_ PATH)_
Public cFileName As String

<MarshalAs(Unma nagedType.ByVal TStr, sizeconst:=14)_
Public cAlternate As String
End Structure

Private Declare Function FindClose Lib "kernel32" (ByVal hFindFile
As IntPtr) As Boolean

Private Declare Auto Function FindFirstFile Lib "kernel32" ( _
ByVal lpFileName As String, _
ByRef lpFindFileData As WIN32_FIND_DATA ) As IntPtr

Private Declare Function FindNextFile Lib "kernel32" ( _
ByVal hFindFile As IntPtr, _
ByRef lpFindFileData As WIN32_FIND_DATA ) As Boolean

This set of declares seems to work for me. Try them out and see what
you get...

--
Tom Shelton

[Lance]

Beautiful. That works perfectly. Thanks so much Tom!

Lance

"Tom Shelton" <to*@mtogden.co mwrote in message
news:11******** *************@7 4g2000cwt.googl egroups.com...

>
Lance wrote:

>Thanks Tom. Remember, WIN32_FIND_DATA as a class caused the "FatalExecution EngineError
"
using your declarations, but as a structure, it was running (although the output of the
members didn't seem to jive).

Private Const MAX_PATH As Integer = 260

' if you using vb2005, you can acually use
System.Runtim.I nteropServices. ComTypes.FILETI ME
<StructLayout(L ayoutKind.Seque ntial)_
Private Structure FILETIME
Public dwLowDateTime As Integer
Public dwHighDateTime As Integer
End Structure

<StructLayout(L ayoutKind.Seque ntial, CharSet:=CharSe t.Auto)_
Private Structure WIN32_FIND_DATA
Public dwFileAttribute s As Integer
Public ftCreationTime As FILETIME
Public ftLastAccessTim e As FILETIME
Public ftLastWriteTime As FILETIME
Public nFileSizeHigh As Integer
Public nFileSizeLow As Integer
Public dwReserved0 As Integer
Public dwReserved1 As Integer

<MarshalAs(Unma nagedType.ByVal TStr, SizeConst:=MAX_ PATH)_
Public cFileName As String

<MarshalAs(Unma nagedType.ByVal TStr, sizeconst:=14)_
Public cAlternate As String
End Structure

Private Declare Function FindClose Lib "kernel32" (ByVal hFindFile
As IntPtr) As Boolean

Private Declare Auto Function FindFirstFile Lib "kernel32" ( _
ByVal lpFileName As String, _
ByRef lpFindFileData As WIN32_FIND_DATA ) As IntPtr

Private Declare Function FindNextFile Lib "kernel32" ( _
ByVal hFindFile As IntPtr, _
ByRef lpFindFileData As WIN32_FIND_DATA ) As Boolean

This set of declares seems to work for me. Try them out and see what
you get...

--
Tom Shelton

[Lance]

Herfried,

Thanks for that sample. I downloaded it last night and while it worked, I couldn't
initially wrap my head around it. It seems far, far, far different than any tutorial,
help file, and example that I have ever seen before. Because it seems to work so well, it
really makes me scratch my head as to why nothing like it is presented anyplace else.
They're always pushing the use of the GetFiles method. That's sort of frustrating. I
thought I was thinking outside the .Net box by going with the API, but this native .Net
method that you suggest is even further outside the box, IMO.

For now, I think I'm going to stick with the API method, as I can understand most of it.
But I'm going to play around with the code you linked to. Once I can figure out how to
debug it and then step through the code, I'm sure I will have learned a lot.

Thanks,
Lance

"Herfried K. Wagner [MVP]" <hi************ ***@gmx.atwrote in message
news:e2******** ******@TK2MSFTN GP02.phx.gbl...

"Lance" <nu***@business .comschrieb:

>I'm working on a program that requires searching multiple drives for multiple file
types and cataloging them based on certain geospatial attributes. All together, there
are hundreds of thousands of files on the drives. As part of the process, I'm
currently using the GetFiles method of the FileSystem object to retrieve collection of
strings representing a collection of a particular file type (for example, tif files).
The problem is that the GetFiles method doesn't seem to make any callbacks that would
allow for me to show some sort of meaningful progress, and the process can take a very
long time.

<URL:http://dotnet.mvps.org/dotnet/samples/filesystem/FileSystemEnume rator.zip>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>

[Tom Shelton]

Herfried K. Wagner [MVP] wrote:

"Lance" <nu***@business .comschrieb:

I'm working on a program that requires searching multiple drives for
multiple file types and cataloging them based on certain geospatial
attributes. All together, there are hundreds of thousands of files on the
drives. As part of the process, I'm currently using the GetFiles method
of the FileSystem object to retrieve collection of strings representing a
collection of a particular file type (for example, tif files). The
problem is that the GetFiles method doesn't seem to make any callbacks
that would allow for me to show some sort of meaningful progress, and the
process can take a very long time.

<URL:http://dotnet.mvps.org/dotnet/samples/filesystem/FileSystemEnume rator.zip>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>

Herfried, that is a very nice (and clever) example of using asnyc
delegates. You are to be commended. But, it still doesn't really
solve the problem - simply because at the heart it still calls
GetFiles. And as much as I love GetFiles, it still returns all the
files in the directory in one chunk. Normally, this isn't an issue.
But, if you have a directory with thousands of files in it, then you
still have to wait for GetFiles to return until you can cancel your
operation, or present any progress, or do any real filtering.

The only way to really get "real time" progress that I know of is to
use the API calls, since you iterate one file at a time, not a whole
directory at a time...

--
Tom Shelton