8 Web Services as Objects
Web services provide a platform-neutral means of exchanging data between two systems over the Web using XML. Simple Object Access Protocol (SOAP) is a standard used to serialize and transfer object data between these systems. ASP.NET goes a long way to isolate programmers from the actual XML and allows them to concentrate on the implementation in the familiar realm of object-oriented code.
Although it's possible to simulate full object orientation in the design of Web services, consideration should be given to make them act as endpoints for the exchange of data, similarly to the way you'd call a static method from a local class. You can also package data in container classes. It's important to consider the performance implications of a Web service that needs to make many calls back and forth to arrive at an end result, as this kind of solution would not scale well.
Consuming a Web service from Visual Studio 2005 requires little more than adding a reference to the Web service. In a Web project, this reference is created dynamically, while a class library creates a physical proxy class. In both scenarios, you can code against these objects as if they were locally in your own system, releasing you from the details of how the data is exchanged with the remote system.
9 The Nuts and Bolts of IIS and Web Applications
Internet Information Services is the part of the Windows operating system that services requests to your Web site. The IIS Manager shows a tree of sites grouped under the Web Sites group. Each site is set to take requests by IP address, port (normally port 80), and a host header value, which allows one IP to be used for several sites.
When an HTTP request arrives at the machine, IIS determines which application will handle the request based on the file extension of the request. If no matching extension is found, the requested file is served straight, the file is served without any processing. These applications that handle the various file types are known as ISAPI applications (Internet Server Application Program Interface).
IIS first gets the request and figures out which ISAPI program will process the page. In the case of ASP.NET, it makes its way to aspnet_isapi.dll and is processed.
ASP.NET compiles pages in one of several different physical file schemes and caches that code for execution in other requests. Of the different schemes possible, inline code and code-beside are the easiest and most practical means of writing and maintaining code.
The pre-compilation performed by the publishing utility can ease deployment by hiding your code, checking for errors, and avoiding the first-run compilation process on the first request.
10 Test, Test, and Retest with All Stakeholders
In my frequently less-than-humble opinion, testing actually begins with the development of specifications and requirements. Before any developer types \class\exactly what your application is supposed to do. This requires involvement from every stakeholder in the process. End-users, subject matter experts (generally the \ese people should stay involved throughout the entire process. It's easier to view development as an evolutionary process than getting a sign-off at the start of the project and delivering what you think they wanted.
Using test-driven development (TDD) principles (more on that in a moment), you'll write tests before the actual code. These tests are frequently simple enough that requirements analysts (yeah, that might be the same person as you) can read the code to understand what's going on and determine whether they match the stated goals or use cases of the application's function.
As development progresses, your suite of tests must still pass. If one or more of the tests fails, you'll have to revisit the code and fix it so that it passes the tests. This absolutely must not be a process that comes when you're \
When the code is closer to \traditional testing and use human beings to find out if your user interface does what it should (along with automated tools such as ACT). The theory is that your underlying business logic already works because you've been testing it all along.
Right up to the end of this process, to the release of the greatest software ever, all your stakeholders should be involved to make sure that the application performs as it should.
11 Accessing a Relational Database
All databases applications have the following structure: n Database client n Database server n Database
The database client is the user application that provides the interface to the system. Often
it is a GUI application that allows users to query and update the database. SQL
SQL stands for Structured Query Language. It is a standard way for database clients to communicate
with varied vendor database systems that implement this standard. The database client will communicate with the database server via SQL statements. Figure
12.5 displays a general solution to the database client/server model.
SQL User DB Client DB Server DB Driver