Tip 184: Creating a List of Directories and Files in a List Box Control

December 5, 1995

Abstract
This article explains how you can easily recreate the structure of a disk
by storing a list of drives, directories, and/or files in a List Box
control.

Creating a List of Directories and Files
The Microsoft? Windows? application programming interface (API) SendMessage
function allows you to store a list of drives, directories, and/or files in
a List Box control. In effect, this lets you easily recreate the structure
of a disk. Although Microsoft Visual Basic? provides the Common Dialog File
and Drive controls, it is faster and easier to use the SendMessage function
to store a list of files in a List Box control. This technique also gives
you greater control and flexibility when manipulating the filenames stored
in the List Box control.

To use the SendMessage function, you must include the following Declare
statement in your project:

Private Declare Function SendMessageAny Lib "user32" Alias "SendMessageA"
   (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Integer,
   lParam As Any) As Long

The SendMessage function is used to send a specific message to a window. In
the example program below, the LB_DIR message is sent to the program's
window. The LB_DIR message tells Windows to add a list of the files
(specified by the wParam argument) to the List Box control.

The wParam argument for the LB_DIR message lets you specify the type of
files you want the List Box control to contain. You can set the wParam
argument to include normal, read-only, hidden, system, and archive files.
In addition, you can also set the wParam argument so that it sends drive
and directory files to the List Box control.

Example Program
This program shows how to create a list of files and/or directories in a
List Box control.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following Constant and Declare statements to the General
    Declarations section of Form1 (note that the Declare statement must
    be typed as a single line of code):

Private Declare Function AppendMenu Lib "user32" Alias "AppendMenuA"
   (ByVal hMenu As Long, ByVal wFlags As Long, ByVal wIDNewItem As Long,
   ByVal lpNewItem As String) As Long
Const WM_USER = &H400

Const LB_DIR = &H18D
Const DIR_NORMALFILES = &H0
Const DIR_READONLY = &H8001
Const DIR_HIDDEN = &H8002
Const DIR_SYSTEM = &H8004
Const DIR_DIRECTORIES = &H8010
Const DIR_ARCHIVED = &H8020
Const DIR_DRIVES = &HC000

 3. Add a Command Button control to Form1. Command1 is created by default.
 4. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    Call ListFiles("c:\*.*")
End Sub

 5. Add a List Box control to Form1. List1 is created by default.
 6. Create a new subroutine called ListFiles. Add the following code to
    this subroutine:

Sub ListFiles(sFileSpec As String)
    Dim I As Long
    List1.Clear
    I = SendMessageAny(List1.hWnd, LB_DIR, DIR_DRIVES, ByVal sFileSpec)
    I = SendMessageAny(List1.hWnd, LB_DIR, DIR_DIRECTORIES, ByVal sFileSpec)
    I = SendMessageAny(List1.hWnd, LB_DIR, DIR_NORMALFILES, ByVal sFileSpec)
End Sub

Run the example program by pressing F5. Click the Command Button control.
The List Box control is filled with the names of your disk drives,
directories, and files.