Enumerating the list of DSN's set up on a computer

Question

I have an Excel application in which I want to present the user with a list of the Data Source Names (ie: DSN's), whereby s/he can choose what data source to use.

Hopefully once I've got the list, I can easily access the DSN properties to connect to the appropriate database.

Please note, I do not want to use a DSN-less connection.

Answer 1

The DSN entries are stored in the registry in the following keys.

HKEY_CURRENT_USER\Software\ODBC\ODBC.INI\ODBC Data Sources
HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBC.INI\ODBC Data Sources

This contains the list of all defined DSN. This acts as an global index and the specific details for each DSN are stored in a key with the DSN name under:

HKEY_CURRENT_USER\Software\ODBC\ODBC.INI
HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBC.INI

Create some entries in both User DSN and System DSN tabs from Data Sources (ODBC) control panel applet and check how these values are stored in the registry.

The following example enumerate the DSN defined for the user trough Control Panel > Administrative Tools > Data Sources (ODBC) [User Dsn Tab].

http://support.microsoft.com/kb/178755

  Option Explicit

  Private Declare Function RegOpenKeyEx Lib "advapi32.dll" _
      Alias "RegOpenKeyExA" _
      (ByVal hKey As Long, _
      ByVal lpSubKey As String, _
      ByVal ulOptions As Long, _
      ByVal samDesired As Long, phkResult As Long) As Long

  Private Declare Function RegEnumValue Lib "advapi32.dll" _
      Alias "RegEnumValueA" _
      (ByVal hKey As Long, _
      ByVal dwIndex As Long, _
      ByVal lpValueName As String, _
      lpcbValueName As Long, _
      ByVal lpReserved As Long, _
      lpType As Long, _
      lpData As Any, _
      lpcbData As Long) As Long

  Private Declare Function RegCloseKey Lib "advapi32.dll" _
      (ByVal hKey As Long) As Long

  Const HKEY_CLASSES_ROOT = &H80000000
  Const HKEY_CURRENT_USER = &H80000001
  Const HKEY_LOCAL_MACHINE = &H80000002
  Const HKEY_USERS = &H80000003

  Const ERROR_SUCCESS = 0&

  Const SYNCHRONIZE = &H100000
  Const STANDARD_RIGHTS_READ = &H20000
  Const STANDARD_RIGHTS_WRITE = &H20000
  Const STANDARD_RIGHTS_EXECUTE = &H20000
  Const STANDARD_RIGHTS_REQUIRED = &HF0000
  Const STANDARD_RIGHTS_ALL = &H1F0000
  Const KEY_QUERY_VALUE = &H1
  Const KEY_SET_VALUE = &H2
  Const KEY_CREATE_SUB_KEY = &H4
  Const KEY_ENUMERATE_SUB_KEYS = &H8
  Const KEY_NOTIFY = &H10
  Const KEY_CREATE_LINK = &H20
  Const KEY_READ = ((STANDARD_RIGHTS_READ Or _
                    KEY_QUERY_VALUE Or _
                    KEY_ENUMERATE_SUB_KEYS Or _
                    KEY_NOTIFY) And _
                    (Not SYNCHRONIZE))

  Const REG_DWORD = 4
  Const REG_BINARY = 3
  Const REG_SZ = 1

  Private Sub Command1_Click()
     Dim lngKeyHandle As Long
     Dim lngResult As Long
     Dim lngCurIdx As Long
     Dim strValue As String
     Dim lngValueLen As Long
     Dim lngData As Long
     Dim lngDataLen As Long
     Dim strResult As String

     lngResult = RegOpenKeyEx(HKEY_CURRENT_USER, _
             "SOFTWARE\ODBC\ODBC.INI\ODBC Data Sources", _
              0&, _
              KEY_READ, _
              lngKeyHandle)

     If lngResult <> ERROR_SUCCESS Then
         MsgBox "Cannot open key"
         Exit Sub
     End If

     lngCurIdx = 0
     Do
        lngValueLen = 2000
        strValue = String(lngValueLen, 0)
        lngDataLen = 2000

        lngResult = RegEnumValue(lngKeyHandle, _
                                 lngCurIdx, _
                                 ByVal strValue, _
                                 lngValueLen, _
                                 0&, _
                                 REG_DWORD, _
                                 ByVal lngData, _
                                 lngDataLen)
        lngCurIdx = lngCurIdx + 1

        If lngResult = ERROR_SUCCESS Then
           strResult = strResult & lngCurIdx & ": " & Left(strValue, lngValueLen) & vbCrLf
        End If
     Loop While lngResult = ERROR_SUCCESS
     Call RegCloseKey(lngKeyHandle)

     Call MsgBox(strResult, vbInformation)
  End Sub