The LA Fox Developer Newsletter

December 2000

Getting Ready for “.NET”...Part 2

The Programmable Web: Web

Services Provides Building

Blocks for the

Microsoft .NET Framework

By Mary Kirtland

(SUMMARY: Web Services are building blocks for constructing

distributed Web-based applications in a platform, object model,

and multilanguage manner. Web Services are based on open

Internet standards, such as HTTP and XML, and form the basis

of Microsoft’s vision of the programmable Web. This article

defines Web Services and the key enabling technologies that

ensure services can be aggregated into applications. It then

describes Microsoft’s new Microsoft. NET Framework and its

support for creating and consuming Web Services. This is the

concluding part of an article begun last month in The Devel-

oper.]

Win Forms Application Model

Conceptually, on top of the services framework sit two applica-

tion models: the Windows® application model and the Web

application model. Although I’ve focused on the Microsoft .NET

Framework as a way to develop Web Services and Web appli-

cations, the framework can also be used to develop more

traditional Windows-based applications (of course, these

applications can use Web Services, too).

Developers writing client applications for Windows can use the

Win Forms application model to take advantage of all the rich

user interface features of Windows, including existing ActiveX

controls and new features of Windows 2000, such as transpar-

ent, layered, and floating windows. Either a traditional Windows

or Web appearance can be selected. Developers will find the

Win Forms programming model and design-time support very

intuitive, given its similarities to existing Windows-based forms

packages.

Win Forms also takes advantage of the Microsoft .NET Frame-

work runtime to reduce total cost of ownership for Windows-

based client applications. The framework security model can

safely execute applications and components on client machines

provided they are written using the Win Forms model or used

from a Win Forms application. If implemented or used in this

way, the cute game someone got off the Internet won’t corrupt

configuration information and data, or automatically send e-mail

to everyone in the user’s address book.

The Microsoft .NET Framework assembly model simplifies

application deployment and versioning. Applications can be

configured to use the versions of shared components they were

built and tested with, rather than using whatever component

versions happen to be installed on the client machine, improving

application reliability and eliminating one of the major causes of

application support calls: incompatible versions of user interface

controls and other shared components.

A Model for Web Applications

Web applications built on the Microsoft NET Framework share

a common application model. In this model, a Web application

is a set of URLs rooted at some base URL. Thus it encom-

passes both Web applications that generate pages for display

in a browser and Web Services. In this section, I’ll detail the

Web application programming model called Active Server

Pages+ (ASP+), which is illustrated in Figure 5.

Figure 5 ASP+ Web Application Model

As you might guess from the name, ASP+ evolves from Active

Server Pages. ASP+ takes advantage of the common language

runtime and services framework to provide a reliable, robust,

scalable hosting environment for Web applications. ASP+ also

benefits from the common language runtime assembly model to

simplify application deployment. In addition, it provides services

to simplify application development (such as state management

services) and higher-level programming models (such as ASP+

Web Forms and ASP+ Web Services).

At the core of ASP+ is the HTTP runtime, a high-performance

runtime for processing HTTP requests that is based on a low-

level architecture similar to the ISAPI architecture provided by

Microsoft Internet Information Services (IIS). The HTTP runtime,

as you saw in Figure 5, is managed code that runs within an

unmanaged host process, such as lIS on server machines or

Microsoft Internet Explorer on client machines. The HTTP

runtime is responsible for processing all incoming HTTP re-

quests, resolving the URL of each request to an application, and

(Con’t, page 4)

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