VB.NET Language in a Nutshell, Second Edition

Name

ChDrive Procedure

Class

Microsoft.VisualBasic.FileSystem

Syntax

ChDrive(drive)

drive (required; String or Char)

The letter of the drive (A-Z) to set as the new default drive

Description

Changes the current working (default) disk drive

Rules at a Glance

• If a zero-length string is supplied, the drive is not changed.

• If driveletter consists of more than one character, only the first character is used to determine the drive.

Example

The following example demonstrates a utility function that uses ChDrive to determine if a given drive is available. By centralizing the test, this reduces the amount of coding required each time you need to use ChDrive.

Private Function IsAvailableDrive(sDrive As String) _
                 As Boolean
    
   'if an error occurs goto to the next line of code
   On Error Resume Next
    
   Dim sCurDrv As String
    
   'get the letter of the current drive
   sCurDrv = Left$(CurDir, 1)

   'attempt to change the drive
   ChDrive(sDrive)

   'did an error occur?
   If Err.Number = 0 Then
      'no - this drive is OK to use
      IsAvailableDrive = True
   Else
      'yes - don't use this drive
      IsAvailableDrive = False
   End If
   'set the drive back to what it was
   ChDrive(sCurDrv)
        
End Function

The following code snippet shows how this function could be implemented within your application:

   If IsAvailableDrive(sDrv) Then
      ChDrive(sDrv)
   Else
      MsgBox ("Cannot use Drive " & sDrv & ":\")
   End If

Programming Tips and Gotchas

• The current directory is unaffected by the ChDrive procedure.

• Since ChDrive only processes the first letter of the drive string, it’s ...