ASP.NET Directives

There are many directives that you can use in your Web applications. The directive types include application, assembly, control, implements, import, OutputCache, Page, Reference, and Register . Table 23-1 lists some of the most common ones and on which objects they can be used.

Table 23-1: ASP.NET Directives
Directive	Description
`Application`	Used to define application-level attributes
`Assembly`	Links an assembly to the application
`Control`	Used by controls
`Implements`	Allows a page to implement a COM interface
`Import`	Imports a namespace into a page
`OutputCache`	Used to cache pages, controls, or data
`Page`	Defines page-specific attributes
`Reference`	Links another page or control to this page
`Register`	Associates an alias with a user control

The Page directive is probably the most important, and it has some specific attributes, which are listed in Table 23-2.

Table 23-2: Page Directive Attributes
Attribute	Description
`AutoEventWireup`	Sets event postbacks
`Buffer`	Sets up response buffering
`ClassName`	Sets the page class name
`ClientTarget`	Targets user agents where controls should be rendered
`CodeBehind`	Sets the .cs file that runs the code for the page
`Debug`	Sets compiling with symbols
`Description`	Provides a description
`EnableSessionState`	Enables or disables `SessionState`
`EnableViewState`	Enables or disables `ViewState`

Note

ViewState allows controls on a Web page to maintain their values and state between postbacks. When a button is clicked and it results in a round-trip from the client to server, the value of the controls with ViewState enabled will be maintained.