December2000

The LA Fox Developer Newsletter

December 2000

“.NET” (Con? from page 4)

ASP+ Web Services

The ASP+ Web Services infrastructure provides a high-level

programming model for building Web Services with ASP+.

While not required for building a Web Service using the Web

Services Platform, it provides several benefits that simplify

development and uses a programming model that will be very

familiar to developers who have worked with ASP or Visual

Basic. Developers don’t need to understand HTTP, SOAP, SCL,

or any other specifications for Web Services to use this pro-

gramming model. The ASP+ Web Services programming model

is shown in Figure 6.

Figure 6 ASP+ Web Services

Developers can create a Web Service with ASP+ by authoring a

file with the extension .asmx and deploying it as part of a Web

application. The ASMX file either contains a reference to a

managed class defined elsewhere or the class definition itself.

The class is derived from the WebService class supplied by

ASP+. Public class methods are exposed as Web Service

methods by marking them with the WebMethod attribute. These

methods can be invoked by sending HTTP requests to the URL

of the ASMX file. You don’t need to handcraft a contract for your

Web Service. ASP+ inspects the class metadata to automati-

cally generate an SCL file when requested by the caller.

Clients may submit service requests via SOAP, HTTP GET, and

HTTP POST. Conventions are defined for encoding methods and

parameters as query strings for HTTP GET and form data for

HTTP POST. The HTTP GET and HTTP POST mechanisms are

not as powerful as SOAP, but they enable clients that don’t

support SOAP to access the Web Service.

The ASP+ Web Services model assumes a stateless service

architecture. Stateless architectures are generally more scal-

able than stateful architectures. Each time a service request is

received, a new object is created, the request is converted into

a method call, and the object is destroyed once the method call

returns. Services can use the ASP+ State Management ser-

vices if they need to maintain state across requests. Web

Services based on ASP+ run in the Web application model, so

they get all the security, deployment, and other benefits of that

model.

ASP+ Web Services also supplies a tool to generate strongly

typed managed proxies for any Web Service described by an

SCL file. The proxy generator maps messages described in the

SCL file into methods on the generated class. The proxy hides

all the network and marshaling plumbing from the application

code, so using the Web Service looks just like using any other

managed code. The proxy will preferentially use SOAP to

communicate with the Web Service, but also supports the HTTP

GET and HTTP POST mechanisms, so they can be used as

well.

Conclusion

Web Services provide a simple, flexible, standards-based model

for binding applications together over the Internet that takes

advantage of existing infrastructure and applications. Web

applications can be easily assembled with locally developed

services and existing services, irrespective of the platform,

development language, or object model used to implement any

of the constituent services or applications.

The Microsoft .NET Framework provides an application model

and key enabling technologies to simplify the creation, deploy-

ment, and ongoing evolution of secure, reliable, scalable, highly

available Web Services while building on existing developer

skills.

[Maty Kirtland is part of the MSDNArchitecture team, where she

helps create pra ctical guidance for developers who design

applications using Microsoft technologies. She is the author of

Designing Component-based Applications (Microsoft Press,

1998).]

Page 5