Visual Basic Concepts

Developing DHTML Applications

A DHTML application is a Visual Basic application that uses a combination of and compiled Visual Basic code in an interactive, browser-based application. A DHTML application resides on the browser machine, where it interprets and responds to actions the end user performs in the browser.

In its simplest form, a DHTML application can be a single HTML page that uses Visual Basic code and the Dynamic HTML object model to instantly respond to actions that occur on the page. This could involve responding to user-initiated actions such as mouse movements and clicks, or responding to actions the browser itself performs, such as opening the page or loading a picture. These are just a few of the things you could do with a more complicated DHTML application:

• Retrieve data from the page and use it to query a database.

• Update the page's appearance and behavior.

• Create HTML elements and insert them onto a page in response to user requests.

DHTML applications use Visual Basic code to perform much of the same processing you might have previously done with script, CGI processing, and other methods of Internet application development — and much of it can be done without transferring processing to the server.

DHTML applications are named for Dynamic HTML, a technology extension of Internet Explorer 4.x that allows developers and end users to interact with Web pages in new ways. DHTML applications must be run on Internet Explorer 4.x.

This chapter assumes that you are familiar with some basic Internet concepts that are covered in "Introduction to Internet Applications." See it for more information on Internet technologies in general, including , the Internet development environment, and models of Web browser and Web server interaction.

Topics

	What is a DHTML Application Introduces and defines DHTML applications, explains their advantages, and presents the structure of a typical application.
	Dynamic HTML in Visual Basic Presents information about how Dynamic HTML is used in DHTML applications and introduces the object model.
	Design Considerations for DHTML Applications Presents considerations to keep in mind when creating your DHTML applications.
	DHTML Application Development Process Presents detailed instructions on how to create DHTML applications.
	Beginning Your DHTML Application Project Presents instructions on how to start a DHTML application.
	Designing Pages for DHTML Applications Explains how to create the user interface for DHTML applications, either by importing an existing HTML page or creating your own in Visual Basic.
	Writing Code Using Dynamic HTML Presents information on how to write code for a DHTML application using the Dynamic HTML object model.
	Managing State in DHTML Applications Explains how to manage state in a DHTML application.
	Testing Your DHTML Application Covers how to test and debug your DHTML applications.
	Building Your DHTML Application Discusses compiling your DHTML applications.
	Deploying Your DHTML Application Presents information on how to deliver your DHTML application to the Web server and to your users.

Sample Applications

DhShowMe.vbp Demonstrates several techniques for incorporating Dynamic HTML functionality into the Web pages you create for DHTML applications and into your Visual Basic code. The pages in this application demonstrate how you can use Dynamic HTML to change the styles, layout, and elements on your Web pages, and how you can use the object model to handle events at multiple levels of the page. You will find DhShowMe.vbp listed in the directory.

PropBag.vbp Demonstrates how to use the GetProperty and PutProperty functions to save state between your Web pages in a DHTML application. You will find PropBag.vbp listed in the directory.