Microsoft KB Archive/291575

= How To Use Visual Basic to Locate CD-ROM Drives =

Article ID: 291575

Article Last Modified on 4/5/2006

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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

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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 &quot;kernel32&quot; Alias &quot;GetDriveTypeA&quot; _ (ByVal nDrive As String) As Long

Private Declare Function GetLogicalDriveStrings Lib &quot;kernel32&quot; _ Alias &quot;GetLogicalDriveStringsA&quot; _ (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 = &quot;&quot; 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 = &quot;&quot; Then ' No drives were found MsgBox &quot;No Drives were found!&quot;, 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 &quot;CD-ROM found at drive &quot; & 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.

