Anatomy of an ASP.NET Page

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Compiling an ASP.NET Page An ASP.NET page is compiled when it is

rendered for the first time A page is compiled to a class that

derives from Page Parse the .aspx file and create a class that

derives from Page The preceding class is then compiled to an

assembly This process is transparent

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Compiling an ASP page(Illustration)

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IIS File Mappings .asax – application files .ascx – ASP user controls .asmx – Web services .aspx – ASP.NET Web pages

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Processing Directives Processing directives are used to

configure the runtime environment Directives can appear anywhere on a page

but best practices dictate that they appear at the beginning of the page

Directives begin with <%@ and end with %> Make sure you don’t forget the %>

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Processing Directives Processing directive are used to

configure the runtime environment Processing directives have the following

format:<%@ directive_name attribute=“value” attribute=“value” %>

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Processing Directives (@ Page) It can appear only in .aspx pages Attributes are divided into roughly three

categories Compilation Page behavior Page output

There are other tools to configure the same options beyond processing directives

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Processing DirectivesPage Compilation See Table 3-5 on page 104 for a

complete list

CodeFile lists the file containing the VB or C# code for the .aspx page

Language describes the programming language for the CodeFile

ClassName explicitly sets the name of the class created upon compilation

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Processing Directives(Referenced Assemblies) Most assemblies are automatically

provided by the compiler Assembly references can also be added

using the @Assembly directive Assembly references can also be added

in the web.config file

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Introduction to the Page Class The Page class provides the basic

behavior for an ASP Web page It’s objects allow you to reference

The application itself (Application) The server itself (Server) The HTTP request (HttpRequest) The HTTP response (HttpResponse) The user’s session (Session)

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Page Class Properties (1) Controls returns a collection of controls on

the page IsPostBack indicates whether the page is

being loaded in response to a postback or is being loaded for the first time

PreviousPage returns a reference to the caller page Only meaningful in case of a cross-page

postback Check IsCrossPagePostback

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Page Class Properties (2) ClientTarget allows you to specify the

type of browser Note that automatic browser detection is

disabled EnableTheming and Theme allows you to

set page themes (more later) MaintainScrollPositionOnPostback

allows the page position to be persisted from one postback to the next

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Page Class Methods (1) DataBind binds all data bound controls

to their data sources (more later) Validate causes validation controls to

validate their data SetFocus sets input focus to the desired

control instance There are methods to work with client

script

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Introduction to Page Events First, this topic is very important to

getting your ASP applications to work ASP uses the eventing model to

Persist state from one postback to the next Create static and dynamic controls Bind control instances to data sources And much more

As your book says “state is an illusion of continuity”

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Page Life Cycle (1) When a page is requested

The runtime figures out why the page is being processed

Normal request Postback Cross-page postback callback

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Page Life Cycle (2) PreInit Event It’s the first event in the page life cycle

Master page has not been associated Themes have not been associated It’s possible to change master page or

theme association at this time IsCallback, IsCrossPagePostback and IsPostBack are set at this time

Control instances have been created

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Page Life Cycle (3) Init Event

Master page and theme have been set and cannot be changed

Child controls are initialized and the ID is set

Child controls are initialized recursively Init event fires for all child controls

before the event fires for the page itself

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Page Life Cycle (4) InitComplete event

Here, viewstate tracking is turn on The event fires only for the page

PreLoad event System initialization is complete We don’t typically do much here

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Page Life Cycle (5) Load event

The event is raised first for the page and then recursively for all child controls

You can access control properties and view state at this time

Create dynamic controls in this event Use IsPostBack to check whether the

page is being loaded in response to a postback or new page

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Page Life Cycle (6) LoadComplete fires after Load

At this point, the page begins its rendering phase

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Page Life Cycle (7) PreRender event

Fires for the page first and then recursively for all controls

Use to update controls before the output is rendered

PreRenderComplete event Raised only for the page after PreRender

has fired for all child control instances

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Page Life Cycle (8) SaveStateComplete event

It fires for all constituent controls and then the page itself Next, the markup is generated

Unload event After rendering, the event fires for all

control instances and then the page itself Use this event to close files or database

connections