FIX: ADO 2.0: Open Connection May Succeed with Invalid Provider (245354)

SYMPTOMS

If you specify a valid OLE DB provider in the ConnectionString property of a Connection object and then try to specify a provider that does not exist (or is otherwise not registered) on the system in the Provider property of the same Connection object, the Open method of the Connection object succeeds against the original provider.

STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

This problem is fixed in Microsoft Data Access Components 2.5 (MDAC 2.5). The latest version of MDAC can be obtained from the following Microsoft Web site:

http://msdn.microsoft.com/dataaccess

MORE INFORMATION

WARNING: Despite the current fix, Microsoft does not recommended that you specify a provider in more than one place while calling the Open method because this behavior might result in unpredictable results.

Steps to Reproduce Behavior

This code only fails on a computer with MDAC 2.1 Service Pack 2 or earlier.

Create a new Standard EXE project in Visual Basic.
On the Project menu, click to select References. Add a reference to Microsoft ActiveX Data Objects 2.1 Library (OLEDB).

Add the following code to your Form1:

Option Explicit

Private Sub Form1_Load()
   Dim cn as ADODB.Connection
   Set cn = new ADODB.Connection

   cn.Open "Provider=SQLOLEDB;Data Source=sqltest;"
   cn.Close

   cn.Provider = "InvalidProvider"
   '  The following line will succeed without MDAC 2.5 or higher
   cn.Open
End Sub