Visual FoxPro 7.0 Ramble on

This year is the year of the development tool Focus Update: Microsoft's Visual Studio.net,borland Delphi 6, Sybase Power Builder 8 have launched either a formal or beta version of our visual FoxPro Of course, it will not miss the industry contest good time, this May, Microsoft released visual FoxPro 7, which is the first visual member of the Fox Family in 1995 visual FoxPro 3 the most revolutionary version.

The term "revolutionary meaning" is not a word I use casually, this is the foreign Fox community to Visual FoxPro 7 general evaluation. Why do you say this, the author will combine the experience of several months to talk about the "revolutionary significance" of the evaluation of understanding. Let's get started!

1. Drive the database with "events"

Every important upgrade in Fox history is related to the database engine, for example, when the standard SQL statements are built in 2.0 and the Magic Index optimization technology is RUSHMORE;3, a complete database and data dictionary concept is presented, incorporating the technology of accessing heterogeneous databases through ODBC; this time 7 as having " "Revolutionary" version upgrades, of course, upgrade the database engine, which is the most beautiful feature of visual FoxPro 7-"Database Container Events" (DB Container Evens). We know that "event-driven" is the mode of operation of the Windows system, and it is a wonderful and powerful way to manage the database with the "event-driven" model. Visual FoxPro 7 defines more than 60 database container events, such as Dbc_activate, dbc_beforeopentable, and gives developers the ability to manage database objects (databases, tables, connections, local attempts, remote views, stored procedures) in a holistic, No matter the size, any operation without escaping the "event" mechanism of monitoring. It can be said that the management of the database in Visual FoxPro 7 has entered a new era.

2. Data processing, or data processing

This is a small change-just add a keyword to the select-sql statement: ReadWrite. It is this small improvement that makes Visual FoxPro's handling of cursor into a "perfect" world! The main feature of Visual FoxPro is that it can be flexible and convenient to operate a large amount of data, this feature in the handling of cursor is the most embodiment. The flexible and robust cursor system is the most distinctive symbol of Visual FoxPro differentiating from other development tools!

We know there are three types of cursor in Visual FoxPro: Updatable cursor, read-write cursor, read-only cursor. "Updatable cursor" means that the data changes on the cursor are updated to the cursor of the data source and belong to this cursor by using the open DBF table, the local and remote views set to "updatable", which are associated with the data source; "Writable cursor" Refers to the fact that the data on the cursor can be maintained, but any data changes will not be updated to the data source, such cursor are mainly generated from local and remote views that do not have "update settings", and cursor obtained directly from heterogeneous databases via SPT; read-only cursor Is the result of the query produced by Select-sql. As the name implies this cursor can only browse, cannot maintain-this is a stumbling block in the complex business system development, the developer hopes to make the data maintenance on the query result, produces the new cursor, again makes the inquiry, again revises. Before Visual FoxPro 7, we usually use the temporary DBF table to solve this problem, because to manually maintain the "intermediate table file", increase disk read and write times, is very troublesome. Now good, readwrite keyword support, make Visual FoxPro super powerful cursor processing more powerful, tend to perfect!

3. XML and Web Service

XML and Web Service are a natural pair, and they may be the hottest technology of the year, and new development tools are available to support them! The Visual FoxPro 7, as a next-generation development tool, certainly has a special focus on XML and Web service, giving Fox developers a powerful and Easy-to-use tool!

Visual FoxPro 7 encapsulates the MSXML Parser with three functions, respectively Cursortoxml (), Xmltocursor (), Xmlupdategram (), which implement the conversion of cursor to XML descriptions, respectively , XML descriptions to cursor transformations, and XML descriptions of data changes in cursor (this feature is designed for SQL Server 2000).

Visual FoxPro 7 support for Web service is implemented through encapsulation of soap (simple Object Access Protocol), embodied in the FFC class library named WEBSERVICES.VCX. Visual FoxPro's support for Web service is divided into two parts: one is to let visual FoxPro act as a client program, then to develop xml-based Web service, and visual FoxPro 7 specifically designed a project Hooks to facilitate developers to quickly develop web Service.

The Web service is a dream for us: Any place, any time, any Internet-accessible (internetable) device can use the services we develop with visual FoxPro. As far as I know, there is a Web service:http://www.foxcentral.net developed with Visual FoxPro, it provides services about Fox Community News, we can see!

To Visual FoxPro 7, Web applications can be implemented at least 5 technologies in Visual FoxPro: Easy to master static Web page publishing through powerful string processing capabilities, and easy to use in active Document for traditional visual FoxPro applications into Web applications, through Foxisapi+visual FoxPro development of COM implementation of Dynamic Web development, through the asp+visual FoxPro development of COM implementation of Dynamic Web page development; and finally, the xml-based web Service.

4. Let Visual FoxPro run as a server

This is Microsoft's ideal, in recent years the Fox development team has mentioned several times: Visual FoxPro will be used as the middle tier of multi-tier applications, my understanding is to let Visual FoxPro run as a server, to provide services to client programs!

There are four important issues that need to be addressed here, and there are satisfactory responses in visual FoxPro 7.

Question one: Can Visual FoxPro develop a stable, efficient server program? Can, in the visual FoxPro SP 3 released in 1999, Microsoft has given visual FoxPro the ability to develop the inner components of multithreaded processes, And added a new Run-time library VFPnT.DLL (n represents version number) to support its run, in this runtime, remove a lot of old-fashioned and interface control elements that make it smaller. However, because the visual FoxPro6 itself is not very stable (plus SP4 or SP5), this great feature is not fully played under visual FoxPro 6 until Visual FoxPro 7 appears to make it appear a hero!

Question two: How to implement distributed transaction and dynamic load balancing? Visual FoxPro 7 has good support for COM +, which can be solved by COM +!

Question three: How does a client Exchange data collection with the server as a server program? This is the Achilles heel of the server program developed by Visual FoxPro 6, and we know that visual FoxPro is used to process data, but not being able to freely exchange data sets with the outside world can greatly reduce the efficiency of development, use, and program operation! In Visual FoxPro 7, our XML can quickly and easily transfer large data sets to truly free the data set. Now back to the visual FoxPro 6 we used the kind of "loop + attributes" approach, there is a feeling of heaven and earth!

Question four: Can you allow Visual FoxPro to develop the server to be used by customers, what do you want to do? You can, in Visual FoxPro 7, provide a completely new function: Execscript (). With it, you can execute multiple client-side statements that conform to the Visual FoxPro specification: You can define variables, do queries, update data, modify table structures ...

Let visual FoxPro run as a server, visual FoxPro 7 did, write this program, it feels good!

5. OLE DB Driver

Here, a bit angry with Microsoft: DBC's OLE DB driver was developed by Microsoft in 1999, but was not dedicated until visual FoxPro 7. However, from now on, Visual FoxPro is also OLE DB Privider, and the effect will be good when you visit the Fox Database with ADO later. This provides easy and efficient access to Fox for Visual Basic and ASP developers! Also, the most obvious change in the OLE DB driver this time than the previous ODBC driver is to support access to the stored procedures in the DBC, which makes it much more resilient to develop the program!

6. Great development Environment

This is visual FoxPro 7 to people the most profound impact of the link, in order to improve the efficiency of development, Microsoft has indeed spent a lot of effort!

IntelliSense. I used to envy Visual Basic programmers, who had the IntelliSense tools in Visual Basic 5 o'clock, so they didn't have to memorize a lot of commands, functions, external ActiveX, COM programming can easily get the object's methods, attributes, Event. In Visual FoxPro, if there is no difficulty in remembering the things of Visual FoxPro itself, it is a headache for ActiveX and COM. Now Visual FoxPro 7 also supports IntelliSense and provides powerful user-defined functionality, which is a configurable tool in visual FoxPro; now visual FoxPro 7 not only supports intelligent input navigation for internal objects, commands, functions, More support for intelligent input navigation for ActiveX, COM, and exciting: Visual FoxPro IntelliSense also supports the latest web Service. You can be proud to say that Visual FoxPro IntelliSense is the best and can be defined by the user.

Object Browse. Like IntelliSense, it has long been in other development environments, but it doesn't reduce my interest in it. First, it's really useful for COM objects, ActiveX observation tools, and most importantly: Visual FoxPro 7 's object Browse is tightly integrated with the visual FoxPro development environment--it's easy to get from the object In the browse, drag-and-drop COM object interface to the program, it is very simple to "implement" COM object interface.

Document View. This is an auxiliary tool for program editing that lists all the procedures, methods, functions, macro definitions, and headers in a file to help programmers navigate quickly in large amounts of code.

The task list is a intimate design that functions like a "bookmark". But what's more powerful than "bookmarks" is that once you close the file "bookmark" It is released and the task List does not. Any time you click the task List item, you can quickly open the file and navigate to the relevant location.

In the above, the author tries to analyze the visual FoxPro 7 is a product with "revolutionary significance" from the angle of technology. Visual FoxPro is really a great development tool that allows you to easily develop desktops, c/S, WEB base applications that are unique to the visual FoxPro--flexible and robust!

Each time you write an introductory article on this type of Visual FoxPro, in the end, always attach a vision of Fox's future, hoping to plug those who say "Visual FoxPro to eliminate" the "Smelly Mouth"!
At the "VFP DevCon 2001" Meeting held in the United States on September 10, 2001, Microsoft's Fox team showcased the next version of Fox in a lecture titled "Visual FoxPro 7.0 and Beyond" (Visual FoxPro 8 Some of the features have been formed, including the WinXP interface style of the full support, from the incremental field, and so on, the specific content you can watch live video online: http://msdn.microsoft.com/vfoxpro/; about the future of Visual FoxPro , Microsoft has a specific commitment. Steve Ballmer, Microsoft's chief executive, delivered a speech this September: We ' re committed to continually improving our tools to match your evolving as demands ation Builders. More specifically, you can refer to the video: http://msdn.microsoft.com/vfoxpro/prodinfo/ballmer.asp.

A little bit of communication with you about the visual FoxPro 7 problem, I hope to have the opportunity to further explore specific issues!