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Writing a File Dialog Box

By Anne-Marie Wright

Although there is a common dialog box control with VB, it is not always what we want. In this article we will be emulating the file handling part of the old windows 3.1 file dialog box. You can modify this example to suit your particular needs.

To start with we need to create a form with a drivelist, directorylist, filelist, label and a textbox contol, with 2 buttons. (See picture below)

Set the control up as follows:

Form

Label

TextBox

DirectoryList

DriveList

FileList

Command1 Button

Command2 Button

Now we have the form setup, we need to get the controls interacting with each other.

To link the controls together we will use the following properties:

  • DriveList - Drive
  • DirectoryList - Path
  • FileList - Path

Drive Property (information from MSDN)

Returns or sets the selected drive at run time. Not available at design time.

Syntax

drivelist.Drive [= drive]

Remarks

The valid drives for the Drive property include all drives present in or connected to the system when the control is created or refreshed at run time. The default setting of the Drive property is the current drive.

When reading this property setting, the selected drive is returned in one of the following formats:

  • Floppy disks — "a:" or "b:", and so on
  • Fixed media — "c: [volume id]"
  • Network connections — "x: \\server\share"

When setting this property:

  • Only the first character of the string is significant (the string isn't case-sensitive).
  • Changing the setting for the Drive property invokes a Change event.
  • Selecting a drive that isn't present causes an error.
  • Setting this property also regenerates the drive list, providing a way in code to track network connections added since the control was created.

If the FileName property is set to a qualified network path without a drive designation, the value of the Drive property is a zero-length string (""), no drive is selected, and the ListIndex property setting is –1.

Note: The Drive property returns a different value from the ListIndex property, which returns the list box selection.

(MSDN April 2000)

Path Property (information from MSDN)

Returns or sets the current path. Not available at design time. For the App object, read-only at run time.

Syntax

object.Path [= pathname]

Remarks

The value of the Path property is a string indicating a path, such as C:\Ob or C:\Windows\System. For a DirListBox or FileListBox control, the default is the current path when the control is created at run time. For the App object, Path specifies the path of the project .VBP file when running the application from the development environment or the path of the .exe file when running the application as an executable file.

Use this property when building an application's file-browsing and manipulation capabilities. Setting the Path property has effects on a control similar to the MS-DOS chdir command — relative paths are allowed with or without a drive specification. Specifying only a drive with a colon (:) selects the current directory on that drive.

The Path property can also be set to a qualified network path without a drive connection using the following syntax:

\\servername\sharename\path

The preceding syntax changes the Drive property to a zero-length string ("").

Changing the value of Path has these effects:

  • For a DirListBox control, generates a Change event.
  • For a FileListBox control, generates a PathChange event.

Note: For DirListBox, the return value of Path is different from that of List(ListIndex), which returns only the selection.

(MSDN April 2000)

Now we have had a look at the properties below is the code that links it all together

Option Explicit

Private Sub DirDialog_Change()
    'Set the filelist path to the same path
    filDialog.Path = DirDialog.Path
End Sub

Private Sub drvDialog_Change()
    'Set the directorylist path to the same drive
    DirDialog.Path = drvDialog.Drive
End Sub

Private Sub filDialog_PathChange()
    'Show the path in the forms caption
    Me.Caption = "Dialog Box - [" & filDialog.Path & "]"
End Sub


If we assume that you have changed the drive in the drivelist control (drvDialog), this is what happens.

 Change the drive to D: This causes the drivelist control's 'change' event to be run
drvDialog_Change When the directorylist path is set, it causes a 'change' event in the directorylist control
 dirDialog_Change When the filelist path is set, it causes a 'pathchange' event in filelist control
 filDialog_PathChange The caption on the form is set to display the path

Now all we need to do to finish the dialog box is select the filename and program the buttons

Private Sub filDialog_Click()
    'Display the name in the textbox
    txtFilename.Text = filDialog.FileName
End Sub

Private Sub cmdCancel_Click()
    MsgBox "CANCELLED"
    Unload Me
End Sub

Private Sub cmdOK_Click()
    Dim strMessage
    
    'Display various elements that can be returned from the form
    strMessage = "Drive: " & drvDialog.Drive
    strMessage = strMessage & vbCr & "Path: " & DirDialog.Path
    strMessage = strMessage & vbCr & "Filename: " & filDialog.FileName
    strMessage = strMessage & vbCr & "The lot: "
    'Check the path has a paragraph mark at the end
    If Right(filDialog.Path, 1) = "\" Then
        strMessage = strMessage & filDialog.Path & filDialog.FileName
    Else
        strMessage = strMessage & filDialog.Path & "\" & filDialog.FileName
    End If
    MsgBox strMessage
    Unload Me
End Sub

We have to check the file path because if you are looking a the root of a drive then the path will have a directory character at the end of the path ('\').

Now we have created a simple file dialog box. You can download the completed sample project here.





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