FAQ: ActiveX Data Objects (ADO) Frequently Asked Questions

ID: Q183606

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SUMMARY

This article presents some frequently asked questions about programming ActiveX Data Objects (ADO).


MORE INFORMATION

Q. What are the ActiveX Data Objects (ADO)?

A. ActiveX Data Objects are a language-neutral object model that expose data raised by an underlying OLE DB Provider. The most commonly used OLE DB Provider is the OLE DB Provider for ODBC Drivers, which exposes ODBC Data sources to ADO.

Q. Where can I get ActiveX Data Objects?

A. ADO is part of the Microsoft Data Access Components (MDAC). ADO can be obtained from the Free Downloads page on this Web site:

http://www.microsoft.com /data/download.htm
Q. Where is the documentation that comes with ADO?

A. The documentation that comes with ADO is in html format and can be found by downloading the MDAC Software Development Kit (SDK) from the preceding Web site. Make sure to choose the Microsoft Data Access Components SDK Stand Alone Setup option when downloading MDAC 2.0.

Q. What is Remote Data Service (RDS) for ActiveX Data Objects (ADO)?

A. Remote Data Service (RDS) is used to transport Active Data Object Recordsets from a server to a client computer. The resulting recordset is cached on the client computer and disconnected from the server. RDS uses a subset of the ADO Object model, the ADOR.Recordset, to provide a low-overhead, high-performance way to marshal recordset data over a network or web.

Q. What is the difference between the ADODB and ADOR objects?

A. The ADODB Library contains additional server side objects (Connection, Command, Error, Parameters, and so forth). These are best used within server side components to communicate with the database.

The ADOR Library is a lighter weight client that allows the manipulation of an existing recordset on the client. It does not include the Connection, Command, Error, or Parameters commands. The ADOR functionality is distributed with the ADO client components.

Q. How do I get started using ADO with C++?

A. The best solution is to use #import, which generates very thin classes around the ADO typelib and lets you manipulate them in a syntax very close to the Visual Basic for Applications (VBA) syntax. Most ADO samples are written using VBA, and #import lets you translate with greater ease than, say, using Microsoft Foundation Class (MFC) OLE's COleDispatchDriver or using COM programming directly. The list of Microsoft Knowledge Base articles that follow will help you to use ADO with #import:

ARTICLE-ID: Q174565 FILE: Adovc.exe Demonstrates Using ADO with Visual C++

ARTICLE-ID: Q173645 BUG: Access Violation in Msdaer.dll with _com_error Exceptions

ARTICLE-ID: Q166112 PRB: Conflict with EOF When Using #import with ADO

ARTICLE-ID: Q169496 INFO: Using ActiveX Data Objects (ADO) via #import in VC++

ARTICLE-ID: Q168354 INFO: Underlying OLE and OLE DB Provider Errors Exposed via ADO

In addition, the following articles can be found when searching using Visual C++ as the product that will prove useful to ADO developers:
ARTICLE-ID: Q172392 INFO: Programmer's Guide to Using ADO in Visual C++

ARTICLE-ID: Q167802 SAMPLE: EXCEPTEX Traps MFC and Win32 Exceptions

ARTICLE-ID: Q175784 INFO: Replacing #import's Exception Raising Mechanism
Q. How do I find Microsoft Knowledge Base (KB) articles for ADO?

A. Please refer to the following Web site:
http://support.microsoft.com/ support/

   If you have not been to this site before, you will need to register
   (once) to proceed. After completing registration, select "Support
   Online" to query the entire Microsoft Knowledge Base. Select "ActiveX
   Data Objects", and then enter in the article Q-number (if you know the
   number), appropriate keywords, or text that will help you find the
   article.
Q. How do I determine ADO's capabilities?

A. ADO is dependent upon the data provider it uses. The easiest/quickest way is to check the Supports property to confirm that the connection or recordset you opened supports the functionality you actually need. You should also confirm that the CursorType, and LockType match what you expected. If the underlying provider cannot support the cursor you requested, ADO downgrades these properties to get the cursor that is closest to what you requested. 

   A more in-depth approach involves analyzing the underlying data provider
   you are using underneath ADO. The most common provider is the OLE DB
   Provider for ODBC Drivers that exposes ODBC Data sources to ADO. You can
   use the Properties collection(s) for the Connection, Command, Recordset,
   and Field objects and compare the results displayed there to the OLE DB
   Specification and the OLE DB Leveling Document, both included with the
   OLE DB SDK, available free for download at this URL:
http://www.microsoft.com/data/ oledb/
Note that ADO will not automatically define each value for each property exposed in the collections. The property will only be set when the operation you are performing with ADO actually needs to use that property exposed by the underlying provider. This is for performance, and varies from other object models such as DAO which initialize any and all properties whether the operation you are performing utilizes them or not.


   Using the Recordset.Supports property is the easiest way to verify that
   what you expect is actually what the provider exposed to you, given the
   specific type of connection and recordset you have opened.

Additional query words: kbinf 


Keywords          : kbnokeyword kbADO kbDatabase kbGenInfo kbMDAC200 
Version           : WINDOWS:1.0,1.5,2.0
Platform          : WINDOWS 
Issue type        : kbinfo

Last Reviewed: April 22, 1999