Datasheet

type-checking. Specifically, if you are using VBScript and want to implement error handling in your
pages, you have to use the
On Error Resume Next statement, and follow every component call with a
check to
Err.Number to make sure that the call had gone well.
ASP.NET is a complete revision of ASP that fixes many of its problems. It does not replace ASP; rather,
ASP.NET pages can live side by side on the same server with legacy ASP applications. Of course, you
can also program ASP.NET with C#!
The following section explores the key features of ASP.NET. For more details, refer to Chapters 26,
“ASP.NET Pages” and 27, “ASP.NET Development.”
Features of ASP.NET
First, and perhaps most important, ASP.NET pages are structured. That is, each page is effectively a class
that inherits from the .NET
System.Web.UI.Page class, and can override a set of methods that are
evoked during the
Page object’s lifetime. (You can think of these events as page-specific cousins of the
OnApplication_Start and OnSession_Start events that went in the global.asa files of plain old
ASP.) Because you can factor a page’s functionality into event handlers with explicit meanings, ASP.NET
pages are easier to understand.
Another nice thing about ASP.NET pages is that you can create them in Visual Studio 2005, the same
environment in which you create the business logic and data access components that those ASP.NET
pages use. A Visual Studio 2005 project, or solution, contains all of the files associated with an applica-
tion. Moreover, you can debug your classic ASP pages in the editor as well; in the old days of Visual
InterDev, it was often a vexing challenge to configure InterDev and the project’s Web server to turn
debugging on.
For maximum clarity, the ASP.NET
code-behind feature lets you take the structured approach even fur-
ther. ASP.NET allows you to isolate the server-side functionality of a page to a class, compile that class
into a DLL, and place that DLL into a directory below the HTML portion. A
code-behind directive at
the top of the page associates the file with its DLL. When a browser requests the page, the Web server
fires the events in the class in the page’s
code-behind DLL.
Last but not least, ASP.NET is remarkable for its increased performance. Whereas classic ASP pages are
interpreted with each page request, the Web server caches ASP.NET pages after compilation. This means
that subsequent requests of an ASP.NET page execute more quickly than the first.
ASP.NET also makes it easy to write pages that cause forms to be displayed by the browser, which you
might use in an intranet environment. The traditional wisdom is that form-based applications offer a
richer user interface, but are harder to maintain because they run on so many different machines. For
this reason, people have relied on form-based applications when rich user interfaces were a necessity
and extensive support could be provided to the users.
With the advent of Internet Explorer 5 and the lackluster performance of Navigator 6, however, the
advantages of form-based applications are clouded. IE 5’s consistent and robust support for DHTML
allows the programmer to create Web-based applications that are every bit as pretty as their fat client
equivalents. Of course, such applications necessitate standardizing on IE and not supporting Navigator.
In many industrial situations, this standardization is now common.
22
Chapter 1
05_575341 ch01.qxd 10/4/05 7:03 PM Page 22