The LA Fox Developer Newsletter

February 2000

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 any-

thing related to the Internet, it is almost impossible to do so

without mentioning XML. XML, the Extensible Markup Lan-

guage, 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 docu-

ments.

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:

+ Microsoft Visual FoxPro 6.0

+ Microsoft Data Access Components, which can be down-

loaded from http://www.microsoft.com/data/

+ SQL Server 6.5 or 7.0 with the sample Northwind database

installed

+ A system DSN called TasTrade that points to the TasTrade

Visual FoxPro Sample Database

+ 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

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 compo-

nents.

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

Connection Object

(Con’t, page 7)

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