Knowledge Base

How To Use Visual Basic to Locate CD-ROM Drives

Article ID: 291575

Article Last Modified on 4/5/2006

APPLIES TO

Microsoft Visual Basic 5.0 Professional Edition
Microsoft Visual Basic 6.0 Professional Edition
Microsoft Visual Basic 5.0 Enterprise Edition
Microsoft Visual Basic 6.0 Enterprise Edition

This article was previously published under Q291575

SUMMARY

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.

MORE INFORMATION

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

Start a new Visual Basic Standard EXE project. Form1 is created by default.
Add a new command button (Command1) to Form1.

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

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.

REFERENCES

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

190000 How To Get Started Programming with the Windows API

180766 VBA: Sample Code to Determine CD-ROM Drive Letter

291573 How To Use Visual Basic to List Active Logical Drives

The Visual Basic Programmer's Guide (available on MSDN Online, http://msdn.microsoft.com)

Additional query words: VB CD CDROM Locate Drive Find List

Keywords: kbhowto kbapi kbsample KB291575

Microsoft KB Archive/291575

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