Page #16 (Chapter 1 - Visual Basic and the Web)

	Chapter 1 - Visual Basic and the Web
	Visual Basic Developers Guide to ASP and IIS
	A. Russell Jones

Copyright 1999 SYBEX Inc.

---

	What's the Difference between IIS and DHTML Applications?

	Visual Basic has two built-in kinds of Web projects:

	IIS applications  These applications run on the Web server, under Microsoft's Internet Information Server. You can write Web applications for any kind of browser (or even non-browser) client using an IIS project.

	DHTML applications  These applications run on the client and use the built-in dynamic HTML (DHTML) capabilities of Microsoft's Internet Explorer (IE) browser to provide fast response to user input. These types of applications are well suited to games, simulations, and data-input applications. Unfortunately, they're limited to Internet Explorer version 4 and higher at this time.

	If you're going to write games or applications that need fast response time and don't have heavy database requirements, and all your clients are running the IE browser, DHTML applications can be a good choice. But despite their advantages, I'm not going to discuss them much in this book, as I explain in the following section.

	This Book Concentrates on IIS Applications

	Let me say that again. This book concentrates only on IIS applications. I've chosen to focus on IIS applications for several reasons:

	•		IIS applications run with multiple browsers and multiple versions of those browsers. You can write an IIS application that will run on anything from version 1x browsers all the way to the latest versions, and anything in between. They'll also run on multiple platforms, including the Mac and Unix machines. This makes IIS applications admirably suited for business applications used by clients who may not all be running Windows or have the latest browser.

	•		IIS applications have a single code base. Because the application resides in its entirety on the Web server, you can update the entire application with a single code change. The advantages of this are hard to beat when you realize how often business rules and database requirements change.

	•		There are no client-side installation issues. This alone makes IIS applications worth considering. I'm sure your Information Technology (IT) department won't be excited about supporting a new type of application on every computer in the enterprise. There are also no versioning issues, because you control the only public version of the application.

	•		The application is available from any location. After an IIS application is up and running, any client computer that can connect to the server can run your application. The application may run more slowly over a dial-up connection than over a 100Mbps network connection, but it will run.

	•		A client isn't bound to one computer. You can use sign-on and password or other security measures to identify clients no matter which computer they're running on. That means, for example, that if you built a training application, a person could sign on to your application and begin a lesson in Des Moines, get called overseas, and finish the application from the Netherlands the next day—all without worrying about saving data or installing anything.

	•		All the data is centralized. Your clients won't ever lose data when they use your application (assuming you have backup procedures in place on the server). Additionally, you have the ability to prove (or disprove) how useful your application is to the business because you can (and should) track use of the application down to the page level. This kind of tracking capability is priceless when it comes to justifying the cost of an application.

	Visual Basic's other type of Web project, DHTML applications, are a completely different sort of animal. They're inextricably bound to the IE browser, version 4 and higher. To try to do justice to both DHTML and IIS applications in the same book would do a disservice to both types. Believe me, you'll have enough to keep you busy with IIS applications alone.

	That's probably enough history and introduction, so let's get started. In the next chapter, I'll give you a model so you can see how an IIS application works and how Visual Basic fits into that model.