A Preview of Active Server Pages+

When a page or Web service is first activated by the client, ASP+ dynamically compiles the code, caches it, and then reuses this cached code for all subsequent requests until the original page is changed – at which point the compiled code version is invalidated and removed from the cache. You can see this as a delay the first time that an ASP+ page is executed, while the response to subsequent requests is almost instant.

Because the compilation is to the intermediate language (rather than the processor-level binary code), any language can be used as long as the compiler outputs code in this intermediate language. In fact, a number of independent vendors are already working on different languages (including Cobol).

And, because the intermediate language code is common across languages, each language can inherit from all others and call routines that were originally written in all the other languages. The efficient component management services provided by the runtime also ensure that the compiled code in the page executes much more efficiently than would be possible using the earlier versions of ASP.

A Checklist of the New Features

The major features that ASP+ provides over earlier versions of ASP are:

• Pages that use the new server-side controls to automate state management in the page, and reduce the code you have to write. Because ASP+ pages have a programming model similar to VB Forms, we also refer to ASP+ pages as Web Forms.
• HTML Server-side Controls can be used to generate the HTML elements in the page output, and allow code to be used to set the properties (i.e. attributes) of these controls at runtime. They also allow events raised by the elements to be detected and appropriate code executed on the server in response to these events.
• Rich Controls that run on the server can be used to create more complex HTML elements and objects in the page output. ASP+ includes a calendar control and a range of grid, table, and list controls. These controls can also take advantage of server-side data binding to populate them with values.
• Web Services allow developers to create classes that are generally not rendered as visible output, but instead provide services to the client. For example, they can include functions that return specific values in response to a request.
• Configuration and Deployment is now easier, with the use of human-readable XML-format configuration files. Components no longer need to be registered on the server (no more regsvr32!), and applications can be deployed using file copy commands, the FrontPage server extensions or FTP.
• Application and Session State Management is extended to provide a persistent and more scalable environment for storing values relevant to specific clients and applications. In particular, a user's session state can now easily be maintained in a Web farm.
• Error Handling, Debugging, and Tracing features have been greatly extended and improved. Each page can have its own 'error page', and can also display values that are used in the page code as it executes – providing a 'trace' facility. Debugging can also be carried out across languages – allowing you to single step seamlessly from one language to another, for example from code in a VB page into a C++ component.
• Security Management Features now allow many different kinds of login and user authentication to be used. Instead of the default browser login prompt (with Windows 2000 and NTLM authentication), custom login pages can be created and managed by ASP+. It is also easier to manage users depending on the role or group they belong to.
• Custom Server-side Caching allows developers to store all kinds of values and objects locally on the server for use in ASP+ pages. The runtime can also cache the output from ASP+ pages. This can provide a huge performance boost in situations where a dynamically created page is the same for many visitors, such as a product catalog.
• A Range of Useful Components are shipped with ASP+. These class libraries can help to make writing Web applications easier. Examples include: the 'SendMail' component, encryption/decryption components, components for defining custom performance counters, components for reading and writing to the NT event log, components for working with MSMQ, network access components (replacements for WinInet), data access components, etc.

Features such as the intrinsic Request and Response objects (and the Form, QueryString, Cookies, and ServerVariables collections that they implement) are compatible with earlier versions of ASP. However, they have gained a lot of new properties and methods that make it easier to build applications. There is also access to the ObjectContext object for use by any existing ASP components. However, there are some new methods and properties available for the intrinsic ASP objects, as well as other issues that affect how existing pages, components and applications perform under ASP+. See Appendix A for more details.

ASP+ Pages

ASP+ Pages are described in detail in Chapters 2, 3 and 4. The four big advantages that ASP+ Pages provide are:

• Controls can encapsulate reusable functionality. This allows them to automate and simplify a lot of the common programming tasks, such as state management, validation, data manipulation, etc. that require specific coding in previous versions of ASP.
• Code is 'cleaner' and easier to read. The encapsulation of code in server controls, combined with the ability to use proper event handling techniques in your pages, allows a more structured design. Reusability of previously tested and optimized controls also means that development is faster.
• There is better support for code and user interface development tools. These can provide true WYSIWYG editing of pages, management of controls properties, and easy access to methods and events of the controls.
• It removes the dependency of ASP on non-typed script languages such as VBScript and JScript. Code can be written in any of the ASP+ supported languages, such as Visual Basic, C++, C#, Perl, etc. It can also be written as separate modules and used within the page, rather than as traditional inline code.