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The LA Fox Developer Newsletter
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February 2000
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ADO Quickstart
(Con’t from page 5)
be released in less than two years. ADO 1.0 was primarily limited to working with Active Server pages. Only one OLE DB provider existed, the OLE DB Provider for ODBC Drivers.
ADO (2.1)—Ships with the newest version of Microsoft Web browser, Internet Explorer 5.0. When discussing data or anything related to the Internet, it is almost impossible to do so without mentioning XML. XML, the Extensible Markup Language, is a mark-up language that allows users to create custom tags to describe data. XML is quickly becoming the universal format for storing and streaming data. The primary storage format in Office 2000 for document data will be XML. ADO (2.1) client-side recordsets can be saved as XML documents.
ADO (2.0)—Represented a huge gain in functionality. One of the most notable new features was the ability to create client-side recordsets. To go along with this, also added were the abilities to create filters and indexes, and the ability to sort recordsets. These abilities are very much the same as those that exist with Visual FoxPro cursors. Finally, the ability to persist client-side recordsets was also added. In effect, data could be acquired from a server into a client-side recordset. The client-side recordset could then be saved as a file on the local hard-drive that could be opened at a later time without being connected to the network.
ADO (1.5)—Introduced new capabilities and providers to ADO. Among the new providers was the OLE DB Provider for Jer(the JOLT Provider). The MS Remote Provider, which powers the Remote Data Services (RDS), was introduced as well. This version also introduced the ability to create disconnected recordsets.
What You Need to Get Started
In order to work through the examples presented in this paper, you will need the following:
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Microsoft Visual FoxPro 6.0
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Microsoft Data Access Components, which can be downloaded from http://www.microsoft.com/data/
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SQL Server 6.5 or 7.0 with the sample Northwind database installed
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A system DSN called TasTrade that points to the TasTrade Visual FoxPro Sample Database
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A system DSN called Northwind that points to the SQL Server Northwind database
Why Incorporate ADO into a Visual FoxPro Application?
Have you ever wanted to pass a cursor as an argument to a function or class method? Or have you wanted to pass data to automation server applications such as Microsoft Word or Excel? Perhaps you have created a Visual FoxPro DLL and
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Until now, the world of component-based development has lacked one thing: a method of effectively moving data between processes. Now, whether ADO is hosted by Visual FoxPro, Visual Basic, Excel, or Word, the interface is consistent. The new COM capabilities of Visual FoxPro 6.0 enable creating of ADO recordsets, populating them with data, and passing them to a variety of processes. This all goes to support the strategic positioning of Visual FoxPro, a creator of middle-tier components.
Just about everything in Visual FoxPro is an object, except for reports, menus, and data. One of the biggest feature requests from Visual FoxPro developers has been the ability to work with data as a set of objects. Data objects provide several benefits, including an enhanced event model and the ability to overcome limitations of Visual FoxPro cursors. While many limitations are gone, many benefits of Visual FoxPro cursors have been retained. As you work with ADO, there’s good reason to think are many similarities to Visual FoxPro; ADO is based on the Visual FoxPro cursor engine. So, for those who have wanted data objects in Visual FoxPro, the wait is over with ADO.
ADO is not a replacement for Visual FoxPro cursors. Rather, Visual FoxPro cursors and ADO are complementary. When used together, very powerful applications can result. The following pages detail the ADO object model and the common properties and methods you will work with, including:
Remote Data Services (RDS), technology which allows for the streaming of data over the Internet via HTTP.
VFPCOM.DLL, which enables the handling of COM events in Visual FoxPro.
ADO Integration into Visual
FoxPro
This section has several comprehensive examples on strategies you may employ when integrating ADO into your Visual FoxPro Applications.
ADO Object Model
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Connection Object
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