Visual Basic Concepts

What is an IIS Application?

An IIS (Internet Information Server) application is a Visual Basic application that lives on a Web server and responds to requests from the browser. An IIS application uses HTML to present its user interface and uses compiled Visual Basic code to process requests and respond to events in the browser.

To the user, an IIS application appears to be made up of a series of HTML pages. To the developer, an IIS application is made up of a special type of object called a webclass, that in turn contains a series of resources called webitems. The webclass acts as the central functional unit of the application, processing data from the browser and sending information to the users. You define a series of procedures that determine how the webclass responds to these requests. The webitems are the HTML pages and other data the webclass can send to the browser in response to a request.

IIS Applications vs. ASP Applications

IIS applications bear a superficial resemblance to Active Server Pages applications. Both types of applications present dynamic Web sites and perform their processing on the server rather than the client. However, each has its unique advantages. Active Server Pages are for script developers interested in authoring Web pages, and offer the unique capability of intermingling script with HTML. IIS applications are for Visual Basic developers building Web-based applications, rather than Web pages. IIS applications allow for complicated business processing and easy access from almost any browser or platform.

IIS Applications vs. DHTML Applications

An IIS application is also similar to another type of Internet application you can create in Visual Basic — a DHTML application. Like IIS applications, DHTML applications also allow you to respond to events in an HTML page. However, there are several key differences between the two types of applications:

  • Dependency — DHTML applications are intended for use on intranets, and are dependent on Internet Explorer 4.0 or later, while IIS applications can be used on the Internet or an intranet. End users of an IIS application do not need a specific operating system or browser.

  • Object model — DHTML applications use a different object model than IIS applications to access and work with the elements on an HTML page. While IIS applications use the Active Server Pages object model, DHTML applications use the object model.

  • Location of processing — IIS applications are designed to perform most of their processing on the Web server, but DHTML applications perform most of their processing on the browser machine. You do not create any Web server components when you create a DHTML application.

For More Information   See "A History of Development on the Internet" in Chapter 1, "Introduction to Internet Applications," for more information on the differences between IIS applications and DHTML applications.