 Instead
of enumerating the registry in order to obtain defined ODBC DSN connections available on a system, this method uses the SQLAllocHandle API to
enumerate the data.
The MSDN states that SQLAllocHandle is deprecated and mapped by the
ODBC 3.x Driver Manager to guarantee backward compatibility of ODBC 3.x drivers that are used with ODBC 2.x applications. The Driver Manager
performs this mapping regardless of the version of the application.
The demo retrieves the ODBC User and System DSN connection data using
the SQLDataSources API, after obtaining a handle to the environment via SQLAllocHandle and setting the environment state via SQLSetEnvAttr.
Returned in the SQLDataSources call are both the DSN connection name and the DSN driver description, which are used to populate separate
lists. This code is easily modified to populate other controls, such as a listview or menu, to allow user-selection of existing DSN
connections. |
Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright ©1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
' applications, but you may not reproduce
' or publish this code on any web site,
' online service, or distribute as source
' on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Declare Function SQLDataSources Lib "odbc32.dll" _
(ByVal hEnv As Long, _
ByVal fDirection As Integer, _
ByVal szDSN As String, _
ByVal cbDSNMax As Integer, _
pcbDSN As Integer, _
ByVal szDescription As String, _
ByVal cbDescriptionMax As Integer, _
pcbDescription As Integer) As Long
Private Declare Function SQLAllocHandle Lib "odbc32.dll" _
(ByVal HandleType As Integer, _
ByVal InputHandle As Long, _
OutputHandlePtr As Long) As Long
Private Declare Function SQLSetEnvAttr Lib "odbc32.dll" _
(ByVal EnvironmentHandle As Long, _
ByVal dwAttribute As Long, _
ByVal ValuePtr As Long, _
ByVal StringLen As Long) As Long
Private Declare Function SQLFreeHandle Lib "odbc32.dll" _
(ByVal HandleType As Integer, _
ByVal Handle As Long) As Long
Private Const SQL_MAX_DSN_LENGTH As Long = 32
Private Const SQL_MAX_DESC_LENGTH As Long = 128
Private Const SQL_SUCCESS As Long = 0
Private Const SQL_FETCH_NEXT As Long = 1
Private Const SQL_NULL_HANDLE As Long = 0
Private Const SQL_HANDLE_ENV As Long = 1
Private Const SQL_ATTR_ODBC_VERSION As Long = 200
Private Const SQL_OV_ODBC3 As Long = 3
Private Const SQL_IS_INTEGER As Long = (-6)
Private Sub Form_Load()
GetUserSystemDSN
End Sub
Private Sub GetUserSystemDSN()
Dim hEnv As Long 'handle to the environment
Dim sServer As String
Dim sDriver As String
Dim nSvrLen As Integer
Dim nDvrLen As Integer
'obtain a handle to the environment
If SQLAllocHandle(SQL_HANDLE_ENV, _
SQL_NULL_HANDLE, hEnv) <> 0 Then
'if successful, set the
'environment for subsequent calls
If SQLSetEnvAttr(hEnv, _
SQL_ATTR_ODBC_VERSION, _
SQL_OV_ODBC3, _
SQL_IS_INTEGER) <> 0 Then
'set up the strings for the call
sServer = Space$(SQL_MAX_DSN_LENGTH)
sDriver = Space$(SQL_MAX_DESC_LENGTH)
'load the DSN names
Do While SQLDataSources(hEnv, _
SQL_FETCH_NEXT, _
sServer, _
SQL_MAX_DSN_LENGTH, _
nSvrLen, _
sDriver, _
SQL_MAX_DESC_LENGTH, _
nDvrLen) = SQL_SUCCESS
'add data to the controls
List1.AddItem Left$(sServer, nSvrLen)
List2.AddItem Left$(sDriver, nDvrLen)
'repad the strings
sServer = Space$(SQL_MAX_DSN_LENGTH)
sDriver = Space$(SQL_MAX_DESC_LENGTH)
Loop
End If 'If SQLSetEnvAttr
'clean up
Call SQLFreeHandle(SQL_HANDLE_ENV, hEnv)
End If 'If SQLAllocHandle
'since each DSN returned its corresponding
'driver, and a given driver can be used
'for multiple DSN's, remove any adjacent
'duplicates
RemoveListDuplicates List2
End Sub
Private Sub RemoveListDuplicates(lst As ListBox)
Dim n As Long
If TypeOf lst Is ListBox Then
With lst
If .ListCount > 1 Then
For n = .ListCount - 1 To 0 Step -1
If .List(n) = .List(n - 1) Then lst.RemoveItem n
Next
End If
End With
End If
End Sub |
