DOCUMENT:Q291575  31-MAR-2001  [vbwin]
TITLE   :HOWTO: Use Visual Basic to Locate CD-ROM Drives
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER::5.0,6.0
OPER/SYS:
KEYWORDS:kbsample kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport

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The information in this article applies to:

 - Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
 - Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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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
-----------

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.

REFERENCES
==========

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

   Q190000 HOWTO: Get Started Programming with the Windows API

   Q180766 VBA: Sample Code to Determine CD-ROM Drive Letter

   Q291573 HOWTO: Use Visual Basic to List Active Logical Drives

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

(c) Microsoft Corporation 2001, All Rights Reserved.
Contributions by Gray McDonald, Microsoft Corporation


Additional query words: VB CD CDROM Locate Drive Find List

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Keywords          : kbsample kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbhowto

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