Visual Basic Q&A

Symptoms
If you try to run Structured Query Language (SQL) against an Oracledatabase through Data Access Objects (DAO), you can encounter the followingerror:

Run-Time Error 3024
Couldn’t find file C:\Program Files\DevStudio\VB\<schema name>.mdb.This error occurs when you try to specify a schema name in your SQLstatement and you use DAO with Oracle. The <schema name> in the errormessage is whatever schema name you specified for the Oracle object youreference.
Resolution
If you add the dbSQLPassThrough option to the OpenRecordset method, thesample code in the MORE INFORMATION section of this article runs withouterror. You can use brackets ([ ]) around the table name in the SQL string toavoid the error as well:

sql = “SELECT * FROM [scott.emp]” Also, you can use an advanced data access technology, such as ActiveX DataObjects (ADO) to avoid this error.

Symptoms
According to Microsoft Knowledge Base article 275561?(http://support.microsoft.com/kb/275561/EN-US/) “ACC2000: New Features in Microsoft Jet 4.0″:
To minimize the impact of the increased page size and respond to a long-standing request from developers building applications based on the Microsoft Jet database engine, row-level locking was added to Jet 4.0.However, row-level locking of an Access database is not available with Data Access Objects (DAO) 3.60.
Resolution
To resolve this problem, use ActiveX Data Objects (ADO) to enable row-level locking on an Access database, and then open DAO connections to the database. All subsequent attempts to open DAO connections to the database will respect the locking mode that you set.

Symptoms
If you try to gain access to an Access 2000 or Access 2002 database, you may receive one of the following errors within your Visual Basic program.
If you are using Microsoft ActiveX Data Objects (ADO) (or the ADO Data Control), you receive the following error message:

Run-time error -2147467259 Unrecognized Database Format XXXIf you are using Data Access Objects (DAO) (or the DAO generic Data Control), you receive the following error message:

Run-time error 3343 Unrecognized Database Format XXX
Resolution
Access 2000 and Access 2002 use the Jet 4.0 engine, which creates Jet 4.0 format database files. Jet 3.5 components do not recognize such a format.If you are using ADO, you get error -2147467259 when you try to connect to your Access 2000 or 2002 database through the Microsoft.Jet.OLEDB.3.51 provider.If you are using DAO, you get error 3343 when you use the Microsoft DAO 3.51 Object Library.The DAO generic Data Control does not work against Access 2000 or 2002 databases and always generates error 3343 unless it is used as instructed in the “Resolution” section of this article. This occurs because this control is based on Jet 3.51 and only recognizes Jet 3.51 (or before) database formats.

Symptoms
If you install Data Transformation Services (DTS) Package event handlers in a Visual Basic application, and the package you call uses an Execute Package task to call another package, an Exception Access Violation (AV) similar to the following may occur:

(1:Child Package) SubStep ‘<title of step> Step’ failed with the following error:
Need to run the object to perform this operation
(Microsoft Data Transformation Services (DTS) Package (80040005):
Provider generated code execution exception:EXCEPTION_ACCESS_VIOLATION)The Access Violation occurs when these conditions are true:You use DTS package event handlers in the Visual Basic application.You use a parent DTS package that uses an Execute Package task to call a child DTS package.
Resolution
Threading limitations in the design of Visual Basic 6.0 prevent the nested child package from reporting it’s events up through the parent package’s event handler.

Symptoms
If you attempt to use the Data control to connect to a password-protected Access database at design time, you receive the following error message:

Not a valid passwordSpecifically, this error occurs when you set the RecordSource property of the Data control.
Resolution
To use the Data control with a password-protected Access 2000 or later database, you must set the Recordset property of the data control at run time as follows:In your project, click References from the Project menu, and then select the Microsoft DAO 3.6 Object Library check box.In the Form_Load event of your form that contains the Data control, place the following code where “Data1″ is the name of your Data control. Make sure to change the path, table name, and password in the following code to reference your database.

Private Sub Form_Load()Dim db As DAO.DatabaseDim ws As DAO.WorkspaceDim rst As DAO.RecordsetSet ws = DBEngine.Workspaces(0)Set db = ws.OpenDatabase _(“C:\Atest.mdb”, _False, False, “MS Access;PWD=aaa”)Set rst = db.OpenRecordset(“Table1″, dbOpenDynaset)Set Data1.Recordset = rstEnd Sub

Symptoms
The Microsoft Data Object Libraries may be referenced in your Visual Basic project. When the Package and Deployment Wizard (PDW) is used to build the installation, the PDW scans the project files and determines which dependency files need to be distributed.
This article provides the general information you need to distribute any of the following Data Object Libraries with your Visual Basic project: Microsoft Data Access Objects (DAO) 3.51 Object LibraryMicrosoft Data Access Objects (DAO) 3.6 Object LibraryMicrosoft Remote Data Object (RDO) 2.0Microsoft ActiveX Data Objects (ADO) 2.0, 2.1, 2.5, or 2.6 Library
Resolution
The files are listed in the Setup’s file that is created by the PDW for distribution.
For additional information on how each section in the Setup.lst file is used, click the following article number to view the article in the Microsoft Knowledge Base:
189743?(http://support.microsoft.com/kb/189743/) Description of Setup.lst sections The following sections describe points to be aware of when you distribute any of the Data Object Libraries.
Microsoft Data Access Objects (DAO) 3.51 Object LibraryIntrinsic data control incompatibility with Microsoft Access 2000 (Jet 4.0) If you use the intrinsic data control in your project and you attempt to connect to a Microsoft Access 2000 database, you may receive the following error message:

Unrecognized Database Format This error message occurs because the DAO generic data control is based on Jet 3.51 and does not recognize Jet 4.0 database formats. Access 2000 is a Jet 4.0 format database. Prior to Microsoft Visual Studio 6.0 Service Pack 4 (SP4), the workaround for this problem was to open a recordset with DAO code, and then assign it to the recordset property of a data control. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
238401?(http://support.microsoft.com/kb/238401/) PRB: Unrecognized database format error message when upgrading to Access 2000 This problem does not exist with the data control that ships with Microsoft Visual Studio 6.0 Service Pack 6.
Visual Studio 6.0 Service Pack 6 can be obtained at the Visual Studio 6.0 Service Pack Web site:
http://msdn2.microsoft.com/en-us/vstudio/aa718364.aspx(http://msdn2.microsoft.com/en-us/vstudio/aa718364.aspx)Jet 3.51 OLE DB Provider is not included in MDAC 2.1 or later The Jet OLE DB Provider requires the version number of the provider in order to connect to an Access database. If your application specifies Version 3.51 of the Jet OLE DB provider in a connection string or a UDL, and you install ADO by redistributing MDAC 2.1, you are likely to receive the following error message:

3706: ADO could not find the specified provider This error message occurs because MDAC 2.0 installs version 3.51 of the Jet OLE DB provider while MDAC 2.1 installs version 4.0 of the Jet OLE DB Provider, but does not install version 3.51. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
197902?(http://support.microsoft.com/kb/197902/) PRB: Jet 3.51 OLE DB Provider is not installed with MDAC 2.1 or later
Microsoft Data Access Objects (DAO) 3.6 Object Library DAO version 3.6 is required for applications that use DAO to read and write to Access 2000 databases. If Access 2000 (or DAO 3.6) is already installed on the destination computer, then no additional steps are required. If it is not, it is necessary to distribute DAO 3.6. However, there is currently no redistributable for DAO 3.6. In order to redistribute DAO 3.6, it is necessary to install DCOM, redistribute MDAC 2.1(GA) or later, and ensure that the DAO DLL is also distributed and registered on the destination computer.
For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
233002?(http://support.microsoft.com/kb/233002/) How to redistribute DAO 3.6
Microsoft Remote Data Object (RDO) 2.0 In order for RDO to be properly distributed and installed, ODBC must already be installed on the destination computer. ODBC can be installed through the odbcst32.exe file, which is located in the ODBC Folder under the SQL/i386 directory on Visual Basic 6.0 Disk 2. ODBC can also be installed by including the MDAC redistributable in the distribution that is outlined in the “References” section covering distributing ADO/MDAC. To determine all of the files needed to distribute for RDO to work successfully on a computer that does not have Visual Basic installed, you can generate a dependency (.dep) file with the Package and Deployment Wizard. To generate a dependency file that shows the files needed for RDO when running the PDW, complete the following steps: Create a Standard EXE project in Visual Basic. Form1 is created by default.Add a reference to Microsoft Remote Data Object 2.0.Save this project and run the Package and Deployment Wizard on it.Select the Package option.On the Package Type, choose Dependency File, and then proceed through the wizard to completion. When you are finished, you have a file with a .dep extension that can be opened with Microsoft Notepad. MSRDO20.dll and its dependencies are shown in this file.
You want to ensure that these files are included with the distribution. If these files are not listed on the Included Files dialog box when you run the Package and Deployment Wizard, include them by clicking Add in the dialog box.
Microsoft ActiveX Data Objects (ADO) 2.0, 2.1 or 2.5 Library The PDW does not distribute mdac_typ unless there is a specific reference to an ADO Library (any version) in the project.
You can also add mdac_typ.exe manually by clicking Add in the Included Files dialog box when you run the Package and Deployment Wizard. The wizard uses the MDAC_Typ.exe file in the …\Wizards\PDWizard\Redist folder. Obtain the MDAC Components at the following Microsoft Web site:
http://msdn2.microsoft.com/en-us/data/aa937695.aspx(http://msdn2.microsoft.com/en-us/data/aa937695.aspx) For additional information how the PDW distributes MDAC, click the following article number to view the article in the Microsoft Knowledge Base:
217754?(http://support.microsoft.com/kb/217754/) How to control which MDAC version the Package and Deployment Wizard (PDW) distributes The installation of Microsoft Data Access Components (MDAC) requires that DCOM be already installed on the destination computer: For Windows 95 computers, install DCOM95.For Windows 98 computers, install DCOM98.Download the latest version of DCOM from the following Microsoft Web page:
http://www.microsoft.com/downloads/details.aspx?familyid=08B1AC1B-7A11-43E8-B59D-0867F9BDDA66&displaylang=en(http://www.microsoft.com/downloads/details.aspx?familyid=08B1AC1B-7A11-43E8-B59D-0867F9BDDA66&displaylang=en) If DCOM is not already installed on the destination computer, you may receive one of the following error messages:

Unable to load file ‘msdadc.dll’ to register it
-or-

DLL registration failed For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
191704?(http://support.microsoft.com/kb/191704/) PRB: Unable to load file to register it during setup