ASP.NET Architecture, Part 1 - Applying Page Directives

Most likely if you are a classic ASP developer, you have used directives such as @ Include and @ Language. The @ Include directive instructs the ASP runtime to include a particular file inline with the page. The @ Language directive tells the runtime to employ a specific script interpreter located within the <% %> render blocks. Directives provide easy ways for developers to determine declaratively how various aspects of an application will ultimately behave. For example, in addition to the @ Language directive, classic ASP provided only four directives:

1. @ Codepage Used in globalization to set the code page for an ASP page
2. @ EnableSessionState Used to disable session state for a specified page
3. @ LCID Used to set the locale identifier for an ASP page
4. @Transaction Used to specify how a page participates in COM+ transactions

ASP.NET has added numerous directives for controlling page behavior, page configuration, and many other tasks. Table 6-1 presents a partial list of new directives included with ASP.NET. Note that in the Values column, T/F stands for true or false.

Attribute	Values	Meaning
@ Page	T/F	Defines page-specific attributes used by ASP.NET compilers and the CLR to determine page behavior.
AutoEventWireup	T/F Default is set in the <pages> segment of the Machine.config or Web.config file	Determines whether handlers are set up automatically. Default is true.
Buffer	T/F	Specifies whether rendered output is buffered before sending it to clients, or sent as it is rendered.
ClassName	Can be any class name	Determines name of page when dynamically compiling the page. This works either with or without CodeBehind.
CodeBehind	File name of CodeBehind class	Visual Studio .NET uses this attribute for locating the CodeBehind class and compiling during a build operation. ASP.NET does not use this attribute.
CodePage	Any code page	The same in both ASP and ASP.NET.
CompilerOptions	A string containing valid compiler options	Allows developers to specify compiler options for a specified page.
ContentType	Any valid MIME type	Sets the MIME type for page output.
Debug	T/F Default is set in the <compilation> section of the Machine.config or Web.config file	Determines whether pages are compiled with debug symbols or not. Default is false.
Description	Any string	Provides a text description of the page. The ASP.NET runtime ignores this attribute.
EnableSessionState	T/F Default is set in the <pages> section of the Machine.config or Web.config file	Determines whether a page request initiates a new session and whether or not the page can access or modify data saved in an existing session. Default is true.
EnableViewState	T/F Default is set in the <pages> section of the Machine.config or Web.config file	Specifies whether ViewState is enabled for the page. Default is true.
EnableViewStateMac	T/F Default is set in the <pages> section of the Machine.config or Web.config file	Determines whether ASP.NET executes a machine authentication check on the content of a hidden form field that is used to store ViewState and to ensure it is not modified on the client. Default is false.

Table 1 ASP.NET Page Directives

NOTE: The list of directives in Table 1 is incomplete. Many other equally important directives exist, such as Inherits, ResponseEncoding, LCID, Strict, and Transaction. You can search for these directives in Visual Studio .NET Help.

Here is a brief example of how you would use the Page directive:

<%@ Page debug="true" %>

Another example sets the trace directive:

<%@ Page trace="true" %>

Other directives include the @ Implements directive, employed to implement a defined interface from within an ASP.NET page. In addition, use the @ Register directive to register user controls and custom server controls on an ASP.NET page.

Come back this Friday, 27/02/2004, for part two of ASP.NET Architecture. This is chapter six of .NET & J2EE Interoperability, by Dwight Peltzer (McGraw-Hill/Osborne, ISBN 0-07-223054-1, 2004). Buy this book now.

Next: Code-Behind Feature >>
 

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