How To Use Visual Basic to Locate CD-ROM Drives

You can find the drive letter of any CD-ROM drive on a local computer by using the Win32 API from Visual Basic. This can be useful during scenarios such as program setup and querying a user for media.

You can use the GetDriveType API to determine the type of drive referenced by a drive letter. By combining this API with a list of the active drive letters on a computer, you can search for CD-ROM drives available on that computer. Note that the API does not distinguish between types of CD-ROM drives, so for example, a DVD drive is considered a CD-ROM drive.

The following code sample demonstrates how to search for local CD-ROM drives by using Visual Basic.

Sample Code

1. Start a new Visual Basic Standard EXE project. Form1 is created by default.
2. Add a new command button (Command1) to Form1.
3. Add the following code to Form1's code window:

   Option Explicit
   
   Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA" _
       (ByVal nDrive As String) As Long
   
   Private Declare Function GetLogicalDriveStrings Lib "kernel32" _
       Alias "GetLogicalDriveStringsA" _
       (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long
   
   Const DRIVE_CDROM& = 5
   
   Public Function GetDriveStrings() As String
       ' Wrapper for calling the GetLogicalDriveStrings api
       
       Dim result As Long          ' Result of our API calls
       Dim strDrives As String     ' String to pass to API call
       Dim lenStrDrives As Long    ' Length of the above string
       
       ' Call GetLogicalDriveStrings with a buffer size of zero to
       ' find out how large our stringbuffer needs to be
       result = GetLogicalDriveStrings(0, strDrives)
       
       strDrives = String(result, 0)
       lenStrDrives = result
       
       ' Call again with our new buffer
       result = GetLogicalDriveStrings(lenStrDrives, strDrives)
       
       If result = 0 Then
           ' There was some error calling the API
           ' Pass back an empty string
           ' NOTE - TODO: Implement proper error handling here
           GetDriveStrings = ""
       Else
           GetDriveStrings = strDrives
       End If
   End Function
   
   Private Sub Command1_Click()
       Dim strDrives As String
       
       ' Find out what drives we have on this machine
       strDrives = GetDriveStrings()
       
       If strDrives = "" Then
           ' No drives were found
           MsgBox "No Drives were found!", vbCritical
       Else
           ' Walk through the string and check the type of each drive
           ' displaying any cd-rom drives we find
           Dim pos As Long
           Dim drive As String
           Dim drivetype As Long
           
           pos = 1
           
           Do While Not Mid$(strDrives, pos, 1) = Chr(0)
               drive = Mid$(strDrives, pos, 3)
               pos = pos + 4
               drivetype = GetDriveType(drive)
               If drivetype = DRIVE_CDROM Then
                   MsgBox "CD-ROM found at drive " & UCase(drive)
               End If
           Loop
       End If
   End Sub
    
   					

4. Click Run or press the F5 key to run the project.

Result: Any CD-ROM drives on the computer are displayed by drive letter in a message box.

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base: The Visual Basic Programmer's Guide (available on MSDN Online, http://msdn.microsoft.com (http://msdn.microsoft.com) )