INFO: Using ActiveX Data Objects (ADO) via Visual Basic

• ActiveX Data Objects (ADO) used with: - Microsoft Visual Basic Learning, Professional, and Enterprise

       Editions for Windows, version 5.0
  

SUMMARY

This article discusses what is necessary to take advantage of ActiveX Data Objects (ADO) with Visual Basic.

MORE INFORMATION

What is ADO?

ActiveX Data Objects is a programming model, which means that it is not dependent upon any given back-end engine. Currently, however, the only engine supporting the ADO model is OLE-DB. OLE-DB is currently dependent on ODBC Version 3.0 Administrator and ODBC Drivers. This is accomplished through the OLE-DB Provider for ODBC, often referred to as Kagera. At present Kagera is the only released provider for OLE-DB, but like ODBC Drivers, other OLE-DB providers can be used seamlessly from ADO.

The ADO object model consists of six objects:

• Connection: Represents an open connection, in this case to an OLE-DB datasource that can be an ODBC data source via Kagera.
• Error: Contains details about data access errors, refreshed for each time an error occurs in a single operation involving ADO.
• Command: Defines a specific command you wish to execute against data.
• Parameters: Optional collection off the command object for any parameters you wish to provide to the command.
• Recordset: Represents a set of records from a table, command object, or SQL Syntax. Can be created without any underlying Connection object.
• Field: Represents a single column of data in a recordset.
• Property: A collection of values raised by the provider for ADO.

Installing ADO on your Machine

To properly install ADO on your machine, you will need to install the OLE- DB SDK version 1.1+, Internet Information Server 3.0+, or Visual InterDev 1.0+. This will install both ADO and necessary underlying ADO components. OLE-DB also requires ODBC version 3.0 Components, which are normally installed from Visual C++.

The OLE-DB SDK is available free for download off the Web from http://www.microsoft.com/data/oledb/.

After ADO is installed on your machine, simply create a new project inside Visual Basic, go to the PROJECTS^REFERENCES menu and select the following:

   Microsoft OLE-DB ActiveX Data Objects (1.0) Library

Error Handling

The documentation for the ADO Error object indicates that the Errors Collection will be populated if any error occurs within ADO or its underlying provider. This is somewhat incorrect. Depending on the source of the error, ADO's errors collection may not be populated. You need to check both the VB Error object as well as the ADO Errors collection.

For more information see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q167957
   TITLE     : INFO: Extracting Error Information from ADO in VB

ADO vs. DAO

If you include references to both ADO and DAO in the same project, you will have some difficulty. Both use the same object named Recordset, so the following code is ambiguous:

   Dim r as recordset

   Dim s As ADODB.Recordset
   Dim t As DAO.Recordset

REFERENCES

For more information, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q168342
   TITLE:      INFO: Choosing the Right VB5 Data Access Interface
               (ADO/DAO/RDO)

Keywords          : adoall adoengall adoengdb
Version           : 5.0
Platform          : WINDOWS
Issue type        : kbinfo