Tip 82: Retrieving Multiple Filenames from the Common Dialog Control

* VB-CODE (4)

Abstract
The Common Dialog control in Visual Basic® allows you to display an
Open File dialog box. You can select one or more filenames from the
Open File dialog box to use within your Visual Basic program. This
article explains how you can retrieve multiple filenames from the
dialog box, parse them into separate strings, and display them in a
List Box control.

Parsing Filenames from the Common Dialog Control
In a Visual Basic® application, you can use an Open File dialog box
to allow your users to select a file. Using the Open File dialog box,
users can select the drive and directory, as well as the individual
files they want to use. To select a file, the user simply clicks the
filename. The dialog boxs FileName property can be used in your
program to determine the name of the selected file.

If the Flags property of the Common Dialog control is set to a value
of 512 (&H200), the user can select a group of files to work with. To
select multiple files, the user would hold the Shift key down while
clicking the mouse on each filename. As with selecting a single file,
the FileName property of the dialog box would return the names of all
the selected files. Each filename is separated by a space character.
The InStr function can be used within a Do-While loop to parse, or
extract, each individual filename from the FileName property. Assuming
that the filenames are stored in the string called FileNames, we can
tell the InStr function to search through the string until it finds a
space character. To extract a single filename, you need to first save
the position in the target string that you are starting to search from
(this is the beginning of the filename). Then you would use the InStr
function to search for the first space character in the string. If a
space character is found, you can use the starting position and the
position returned by InStr to extract that single filename.

Example Program

1. Create a new project in Visual Basic. Form1 is created by default.
2. Add a Common Dialog control to Form1. CommonDialog1 is created by
  default.
3. Add a List Box control to Form1. List1 is created by default.
4. Add a Command Button control to Form1. Command1 is created by
  default.
5. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
  Dim DelimPos As Integer
  Dim FileNames As String
  Dim NextName As String

  CommonDialog1.Flags = &H200&
  CommonDialog1.Action = 1
  CommonDialog1.Filter = 1

  FileNames = CommonDialog1.FileName

  Do While Len(FileNames) > 0
      DelimPos = InStr(FileNames, " ")
      If DelimPos = 0 Then
          NextName = FileNames
          FileNames = ""
      Else
          NextName = Mid$(FileNames, 1, DelimPos - 1)

          FileNames = Mid$(FileNames, DelimPos + 1)
      End If
  List1.AddItem NextName
  Loop
End Sub

Run the example program by pressing the F5 function key. Click the
command button to call up the Open File dialog box. Type a filename
such as *.* and click the OK command button. Select several files
from the file list by holding the SHIFT key down and clicking each
individual filename. Click the OK command button when you have
selected several files. The files you selected will be displayed in
the List Box control.