ActiveX Data Objects (ADO) Frequently Asked Questions

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

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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: 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, or the Microsoft Data Access Components SDK Update if downloading MDAC 2.1.

The documentation for the latest version of ADO is also available online at: The documentation for ADO is part of the Platform SDK documentation that comes with the MSDN Library. In the MSDN Library, choose Contents, then Platform SDK | Data Access Services | Microsoft Data Access Components (MDAC) SDK | Microsoft ActiveX Data Objects (ADO).

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 follows will help you to use ADO with #import:
220152 Sample: ADOVC1 Simple ADO/VC++ Application
173645 BUG: Access Violation in Msdaer.dll with _com_error Exceptions
173645 FILE: Adovcbtd.exe #import Using UpdateBatch and CancelBatch
184968 Adovcsp.exe Demonstrates Using Stored Procedures with ADO
182389 FILE: Adovcbm.exe ADO 1.5 with #import and Getrows/Bookmarks
166112 PRB: Conflict with EOF When Using #import with ADO
169496 INFO: Using ActiveX Data Objects (ADO) via #import in VC++
168354 INFO: Underlying OLE and OLEDB Provider Errors Are Exposed Through ADO
Additionally, the following articles can be found when searching using Visual C++ as the product that will prove useful to ADO developers:
167802 SAMPLE: EXCEPTEX Traps MFC and Win32 Exceptions
175784 INFO: Replacing #import's Exception Raising Mechanism
Q. How do I find Microsoft Knowledge Base (KB) articles for ADO?

A. Connect to the Microsoft Knowledge Base on the World Wide Web. To access the Microsoft Knowledge Base on the World Wide Web, visit the following Microsoft Web site: For additional information about how to use the Microsoft Knowledge Base, click the article number below to view the article in the Microsoft Knowledge Base:
129725 Obtaining Knowledge Base Articles on the World Wide Web
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: 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.

Artikel-id: 183606 - Laatst bijgewerkt: 27 mrt. 2007 - Revisie: 1