This article was previously published under Q171146
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SUMMARY
In the 32-bit version of Visual Basic 4.0, it is possible to use DSN-less
connections, but because the 16-bit version of ODBC can not handle this
syntax, it is not possible to do this in the 16-bit version of Visual Basic
4.0. It is possible to emulate this ability by dynamically creating and
removing a Data Source Name (DSN) on the fly using the SQLConfigDataSource
ODBC API call.
The following is a 16-and 32-bit example that demonstrates this technique.
The 32-bit code was included because this technique has other uses as
described below. The 32-bit techniques presented in this article also apply
to Visual Basic 5.0.
The 32-bit ODBC ability to use a DSN-less connection has many uses:
1.
Client Simplicity. The user does not have to worry about setting up a
DSN, naming it correctly, setting up options, etc. All this can be done
dynamically by the application.
2.
It solves many JET engine connection and connect string caching issues.
3.
Increases the flexibility of the application.
All of these uses can be realized in 16-bit ODBC by creating and deleting a
DSN on the fly. This method is also useful for simple DSN management. The
code could be used to automatically create, modify, or delete a DSN at any
time. Visual Basic does provide the ability to create a DSN using the
DBEngine.RegisterDatabase() method, but the API provides greater
functionality and the ability to modify and remove a DSN, as well.
In the Advanced tab of the Options dialog box under the Tools menu, set a Conditional Compilation Argument named WIN32 equal to 1 if using Visual Basic 4.0 32-bit, or 0 if using Visual Basic 4.0 16-bit.
3.
Add two CommandButtons to the default form.
4.
Add the following code to the General Declarations:
Option Explicit
'Constant Declaration
Private Const ODBC_ADD_DSN = 1 ' Add data source
Private Const ODBC_CONFIG_DSN = 2 ' Configure (edit) data source
Private Const ODBC_REMOVE_DSN = 3 ' Remove data source
Private Const vbAPINull As Long = 0& ' NULL Pointer
'Function Declare
#If WIN32 Then
Private Declare Function SQLConfigDataSource Lib "ODBCCP32.DLL" _
(ByVal hwndParent As Long, ByVal fRequest As Long, _
ByVal lpszDriver As String, ByVal lpszAttributes As String) _
As Long
#Else
Private Declare Function SQLConfigDataSource Lib "ODBCINST.DLL" _
(ByVal hwndParent As Integer, ByVal fRequest As Integer, ByVal _
lpszDriver As String, ByVal lpszAttributes As String) As Integer
#End If
5.
Add the following code into the Click event of Command1:
#If WIN32 Then
Dim intRet As Long
#Else
Dim intRet As Integer
#End If
Dim strDriver As String
Dim strAttributes As String
'Set the driver to SQL Server because it is most common.
strDriver = "SQL Server"
'Set the attributes delimited by null.
'See driver documentation for a complete
'list of supported attributes.
strAttributes = "SERVER=SomeServer" & Chr$(0)
strAttributes = strAttributes & "DESCRIPTION=Temp DSN" & Chr$(0)
strAttributes = strAttributes & "DSN=DSN_TEMP" & Chr$(0)
strAttributes = strAttributes & "DATABASE=pubs" & Chr$(0)
'To show dialog, use Form1.Hwnd instead of vbAPINull.
intRet = SQLConfigDataSource(vbAPINull, ODBC_ADD_DSN, _
strDriver, strAttributes)
If intRet Then
MsgBox "DSN Created"
Else
MsgBox "Create Failed"
End If
6.
Add the following code into the Click event of Command2:
#If WIN32 Then
Dim intRet As Long
#Else
Dim intRet As Integer
#End If
Dim strDriver As String
Dim strAttributes As String
'Set the driver to SQL Server because most common.
strDriver = "SQL Server"
'Set the attributes delimited by null.
'See driver documentation for a complete list of attributes.
strAttributes = "DSN=DSN_TEMP" & Chr$(0)
'To show dialog, use Form1.Hwnd instead of vbAPINull.
intRet = SQLConfigDataSource(vbAPINull, ODBC_REMOVE_DSN, _
strDriver, strAttributes)
If intRet Then
MsgBox "DSN Deleted"
Else
MsgBox "Delete Failed"
End If
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