Web II - 02 - How ASP.NET Works

Overview
2

 ASP.NET Event Model
 ASP.NET Code Compilation
 The P Class
Page

 ASP.NET Application Lifecycle

Event Model
3

 One of the key features of ASP.NET is that it uses an
event-based programming model.
 In the simple Hello World example, we added a small
p p ,
bit of programming to a method named Page_Load.
 This method is an event handler.
 An event handler is a method that determines what actions
are performed when an event occurs, such as when the user
clicks a button or selects an item from a list.
 When an event is raised, the handler for that specific event
is executed.

Event Handlers
4

 In the .NET Framework, all event handlers have a
specific method signature, that is, a specific return
type and parameters.
yp p
 Event handlers are always void methods.
 Event handlers always accept two parameters:
 an object parameter
 an EventArgs parameter
 (or
( a subclass of EventArgs, such as CommandEventArgs or
bl f h d
ImageClickEventArgs).

protected void Page_Load(object sender, EventArgs e)
protected void Page Load(object sender, EventArgs e)
{
…
}

ASP.NET Event System
y
5

 The event system in ASP.NET operates in a different
manner than in a Windows application or from the
event system in browser-based Javascript.
y p
 In a Windows application, for instance, events are
raised and handled on the same processor.
 In contrast, ASP.NET events are raised on the client (the
browser) but transmitted to and handled on the server.
 Si
Since its event h dli requires a round-trip to the server,
i handling i d i h
ASP.NET offers a smaller set of events in comparison to a
totally client-based event system.

ASP.NET Event System
y
6

7 HTTP P
Protocol
l
A Di
Digression
i

HTTP
8

 Communication protocol for the web
 Current version HTTP/1.1

HTTP
9

 An HTTP session is a sequence of network request-
q q
response transactions.
 An HTTP client initiates a request.
 Itestablishes a Transmission Control Protocol (TCP) connection
to a particular port on a host (typically port 80)
 An HTTP server listening o that po wa s for a client's
se ve s e g on a port waits o c e s
request message.
 Upon receiving the request, the server sends back
 a status line, such as "HTTP/1 1 200 OK , and
line HTTP/1.1 OK"
 a message of its own, the body of which is perhaps the
requested resource, an error message, or some other information.

HTTP Requests
q
10

 An HTML page, once received, typically will invoke
subsequent HTTP requests for other resources:
<img src="someimage.gif" />
g g g /
<link href="somestyles.css" />
<script src="somecode.js" />
<embed src= someflash.swf />
<embed src="someflash swf" />

1. User makes request
q

2. Browser sends HTTP request to server

Request Line GET /comp1274/randyc/lab10done/enter_country.htm HTTP/1.1
Accept: */*
Accept‐Language: en‐us,en‐ca;q=0.5
Accept‐Encoding: gzip, deflate
Request Header User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322;
User‐Agent: Mozilla/4 0 (compatible; MSIE 6 0; Windows NT 5 1; SV1; NET CLR 1 1 4322;
InfoPath.1; .NET CLR 2.0.50727)
Host: csweb2.mtroyal.ca
Connection: Keep‐Alive
Blank line

HTTP
Request

Browser
owse Web Server
Se ve

3. Server receives and processes the HTTP request

HTTP
Request
Browser Web Server

Retrieve
Requested file

4. Server sends HTTP response back
p
Response Line + Status Code HTTP/1.1 200 OK
Server: Microsoft‐IIS/5.0
Date: Thu, 30 Mar 2006 19:50:54 GMT
Content‐Type: text/html
Response Header
Accept Ranges: bytes
Accept‐Ranges: bytes
Last‐Modified: Fri, 24 Mar 2006 17:50:50 GMT
Content‐Length: 209
Blank line

<html><head><title>Enter A Country</title></head>
<body>
<form method="post" action="form_filter.asp">
Enter Country Search:
y Server
Response Content
<input type="text" name="search"><p>
<input type="submit"> HTTP
</form> Response
</body></html>

Browser

5. Browser displays response
p y p


POST /comp1274/randyc/lab10done/form_filter.asp HTTP/1.1
Accept: */*
A t */*
Referer: http://csweb2.mtroyal.ca/comp1274/randyc/lab10done/enter_country.htm
Content‐Type: application/x‐www‐form‐urlencoded
C t t T li ti / f l d d
User‐Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR
)
1.1.4322; InfoPath.1; .NET CLR 2.0.50727)
Cache‐Control: no‐cache

Search=Canada

User entered form data goes here in the http request header (because form
method="post") as a series of name=value pairs (called a querystring)

What if method=get rather than post?

<form method="get" action="form_filter.asp">

Then the user entered form data is added to the requested URL
GET /comp1274/randyc/lab10done/form_filter.asp?Search=Canada HTTP/1.1

Versus

<form method="post" action="form_filter.asp">

Then the user entered form data is added to the end of HTTP request header
POST /comp1274/randyc/lab10done/form_filter.asp HTTP/1.1
rest of HTTP request header goes here

Search=Canada


HTTP
Request
Browser Web Server

Server processes
the request
h

9. Server script generates response sent back to
browser

HTTP/1.1 200 OK
Date: Thu, 30 Mar 2006 19:51:06 GMT
Cache‐control: private

<html><head><title>reading recordsets</title></head>
<body>
<h2>countries</h2>
<table border=1>
<tr><td>2</td><td>canada</td></tr>
</table>
</body></html>
/b d /ht l

10. Browser displays the response
p y p


GET /comp1274/randyc/lab10done/data_browser.asp HTTP/1.1
Accept: */*
1.1.4322; InfoPath.1; .NET CLR 2.0.50727)


HTTP
Request
Browser Web Server

Server processes
the request
h

4. Server script generates response sent back to browser

HTTP/1.1 200 OK
S Mi ft IIS/5 0
Date: Thu, 30 Mar 2006 19:51:06 GMT
Content Type: text/html

<html><head><title>Data Browser</title></head>
<body>
<h1>SELECT * FROM movies WHERE runtime < 90<h1>
<table border=1>
<tr>
<td><b>Title</b></td>
<td><b>Release Date</b></td>
<td><b>Run Time</b></td>
</tr>
...

p y p

6. User makes request (click on a link)
q ( )


GET /comp1274/randyc/lab10done/movie.asp?ID=84 HTTP/1.1
Accept: */*
Referer: http://csweb2.mtroyal.ca/comp1274/randyc/lab10done/data_browser.asp
1.1.4322; InfoPath.1; .NET CLR 2.0.50727)
y

8. Server receives request, processes it, and generates response

HTTP/1.1 200 OK
Date: Thu, 30 Mar 2006 19:51:06 GMT
/h l

<html><head><title>nightmare before christmas, the</title></head>
<html><head><title>nightmare before christmas the</title></head>
<body>
<h1>Nightmare Before Christmas, The</h1>
Directed by <b>Henry Selick</b><br/>
Released on 12/9/1994<br/>
Movie length is 76 minutes
<h2>Summary</h2>
...

p y p


GET /comp1274/randyc/lab10done/does_not_exist.asp HTTP/1.1
Accept: */*
1.1.4322; InfoPath.1; .NET CLR 2.0.50727)


HTTP
Request
Browser Web Server

Server processes
the request

4. Server receives request, processes it, and generates response

HTTP/1.1 404 Object Not Found
i f /
Date: Thu, 30 Mar 2006 19:51:06 GMT
Content Type: text/html

<html>
...
<title>The page cannot be found</title>
...
<body>
<table>
...
The page you are looking for might have been removed, had its
The page you are looking for might have been removed had its
...

Examining HTTP
g
39

Google Chrome

FireFox Firebug Extension

40 Back ASPNET
B k to ASP.NET
Digression over …
Di i

ASP.NET Event Handling
g
41

 How then does ASP.NET communicate the triggering
of an event on one machine (the client browser’s) to
another machine (the server hosting the page)?
( g p g )
 Answer 1:
 Through HTTP
 Answer 2:
 Through querystring parameters sent via HTTP
 Answer 3:
 Through postback

Postback
42

 Postback is the process by which the browser posts
information back to itself.
 That is, p
, posts information back to the server by
y
requesting the same page.
 That is, it is simply a HTTP POST request for the same
ASP.NET page

Postback
43

<body> EventTest.aspx (on server)
<form id= form1 runat= server >
<form id="form1" runat="server">
Please enter your name:
<asp:TextBox ID="name" runat="server" /><br />
Choose favorite author:
<asp:DropDownList ID="myList" runat="server" >
<asp:ListItem>Choose an author</asp:ListItem>
<asp:ListItem>Atwood</asp:ListItem>
<asp:ListItem>Austin</asp:ListItem>
<asp:ListItem>Hawthorne</asp:ListItem>
<asp:ListItem>Melville</asp:ListItem>
</asp:DropDownList><br />
<asp:Button ID="btnEnter" runat="server" Text=“Enter“
OnClick=“btnEnter_Click" />
<p><asp:Label ID="msg1" runat="server" /></p>
<p><asp:Label ID "msg1" runat "server" /></p>
</form>
</body>

Result in browser
<body>
<form name="form1" method="post" action="EventTest.aspx" id="form1">

<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE"
Q: Which page will be value="/wEPDwUJMzU4OTQyMTQyD2QWAgIDD2Q …
requested when the user …
<input type="submit" name="btnEnter" value="Submit" id="btnEnter" />
presses the submit button? <p><span id="msg1">In Page_Load<br/></span></p>
…

Postback
44

 Postback in ASP.NET
 only occurs within web forms (i.e., within a form element
with runat="server"), and
 only server control events cause a post back.

 Each cycle in which information is displayed then
y p y
posted back to the server, and then redisplayed
again, is sometimes also called a postback round
trip.

Postback
45

 In other words, it is postback which makes it possible
for browser-based events (e.g., clicking a button,
choosing from a list) to be handled on the web
g )
server.

Event Types
yp
47

 Two types
 Page events
 Always
y triggered and always in a certain specific order (see
gg y p (
Page Lifecycle).
 Triggered and handled on the server.
 Thus
Th no postback involved
tb k i l d
 Control events
 Associated with particular controls and only triggered in
certain circumstances.
 Requires postback

Postback and Events
48

 How does the server “know” that a request is a
know
postback request (i.e., a request in which a control
event will have to be handled)?
)
 By the presence of the viewstate variable.

HTTP + Postback
49

First request for page (from URL, or link, bookmark, …)
1
GET http://localhost:53372/Chapter2/EventTest.aspx

NOTE: since this is the first request, there are no querystring parameters in the request

2 Page executes on the server.
HTTP/1.1 200 OK
Server: ASP.NET Development Server/9.0.0.0
Date: Tue, 21 Sep 2010 18:52:36 GMT
C t t th 2039

<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>Event Test</title></head>
<body>
value="/wEPDwUJMzU4 …
...

The generated HTTP response (above) for request contains hidden viewstate

HTTP + Postback
50

3
GET http://localhost:53372/Chapter2/EventTest.aspx
… Second request for page
Name=Randy&myList=Melvillee&__VIEWSTATE=/wEPDwUJMzU4… (from user clicking button)

NOTE: since this is the postback request, there are querystring parameters in the request header,
one of which is the viewstate (as well as user’s form data)
user s

4 HTTP/1.1 200 OK
Server: ASP.NET Development Server/9.0.0.0
Date: Tue, 21 Sep 2010 18:52:36 GMT
Date: Tue 21 Sep 2010 18:52:36 GMT
Server can figure out that this is
<html xmlns="http://www.w3.org/1999/xhtml"> a postback request from the
<head><title>Event Test</title></head> presence of the viewstate
iewstate
<body>
querystring parameter
value="/wEPDwUJMzU4 …
...

HTTP Response for this postback request still contains hidden, but probably modified, viewstate

View State
51

 View state is one of the most important features of
ASP.NET.
 It is a specially encoded string that is used to retain
page and form information between requests and is
sent to the browser within a hidden HTML <input>
element.
 All page elements not posted back via the standard
HTTP POST mechanism are stored within this string.
value= /wEPDwUJODExMDE5NzY5D2QWAgIDD2QWAgIBDw8WAh4EVGV4dAUKMDgvMDE
value "/wEPDwUJODExMDE5NzY5D2QWAgIDD2QWAgIBDw8WAh4EVGV4dAUKMDgvMDE
vMjAwNmRkZDZPhFHJER4chf3nmlgfL+uq4W58" />

View State
52

 View state is a mechanism for preserving display
state within web forms.
 Recall that HTTP is by nature stateless.
 This means that after the server responds to a request,
it no longer preserves any data used for that request.
 Nonetheless, web applications very frequently need
to retain state on a page between requests.

View State
53

 View state is generated once all the page code has
executed but before the response is rendered.
 The value of each web server control on the page is
serialized into text as a number of Base64-
encoded triplets, one of which contains a name-
p
value pair.
 Serialize = convert programming object into some type
of text representation.
 This view state string is then output to the browser
as a hidden <input> element named "__VIEWSTATE".

View State
54

 When the form is posted back, ASP.NET receives the
view state (since it was contained in a form
element), deserializes this information and restores
),
the state of all the controls prior to the post.
 Deserialize = convert some type of text representation
back into a programming object.
 ASP.NET updates the state of the controls based on
the data that has just been posted back, and then
calls the usual page and control event handlers.

View State
55

 Since the details of encoding and decoding values
from the view state are handled by the ASP.NET
runtime, y can g
, you generally ignore the view state
y g
and simply enjoy its benefits.

Viewstate
56

 However, sometimes a developer may wish to turn
off the view state for a page.
 For instance, if a very large data set is being
, y g g
displayed, the view state will also be quite large, which
may significantly lengthen the time it takes the browser
to d
download and render the page.
l d d d h

Large View State
g
57

Viewstate = 277K

Turn Off Viewstate
58

 If a page is not going to post back to itself, you can
improve page performance by disabling the view
state for the page within the Page directive.
p g g
<%@ Page ... EnableViewState="false" %>

 You can also disable viewstate on a control-by-
control by
control basis.
<asp:Label runat="server" ID="Label2" ViewStateMode="Disabled" ... />

Disabling Viewstate
g
59

viewstate = 0.05 K

Disabling Viewstate
g
60

 Do remember that viewstate is required for any
type of postback (control-event) processing.
 Again, you only want to disable it for pages or
controls that don’t need it.

Page Life Cycle
g y
61

 Page and control events occur in a certain order
which we can call the page life cycle.
 Five general stages:
 Page initialization
 Loading

 Postback control event handling

 Renderingg
 Unloading

Complete Page Life Cycle
p g y
62

Event Handlers
63

 Within each of these stages, the ASP.NET page
raises events that you can handle in your code.
 For most situations, you only need to worry about
the Page_Load event and certain control events.

Event Handlers
64

 Because page events always happen, you simply need to
p g y pp , y py
define a page event handler by using the appropriate
naming convention:
 Page_XXXX
Page XXXX where XXXX is the event name
 Control events need to be explicitly wired.
 i.e., you must explicitly bind the handler method to the event.
 This can be done declaratively in the markup (the usual case),

<asp: utto
<asp:Button id="btnSubmit" runat="server"
d bt Sub t u at se e
OnClick="btnSubmit_Click" />

 or programmatically in the code (rare).
btnSubmit.Click += new EventHandler( this.btnSubmit_Click );

Adding Event Handlers in VS
g
65

Detecting Postback
g
66

 There are times when you may want your page to
behave differently the very first time it is requested.
 One typical example is that you want to read and
yp p y
display values from a database in a list only the first
time the page is requested.
 In subsequent postbacks, the data is preserved by the
view state so there is no need to re-read the database.

Detecting Postback
g
67

 Your page can test if it is being requested for the
first time via the IsPostBack property
 Thisp p y
property is equal to false if the page is being
q p g g
requested for the first time.
protected void Page_Load(object sender, EventArgs e)
{
…
if (! IsPostBack)
{
// Do something here for very first request
}
…
}

Postback and Non-Postback Controls
68

 Button-type controls with Click events always generate
an immediate postback to the server.
 But not all control events generate an immediate
postback.
 In fact, most control events by default do not cause a
postback.
 Some controls—for i
S l f instance, a Label control—never can
l
cause a postback.
 Change events also do not generate a postback, by
default.
d f lt
 An example of a change event is selecting an item from a drop-
down list or entering text into a text box.

Change Events
g
69

 You may be able to enable postback for change-
change
type events by setting the control’s AutoPostBack
p p y
property to true.
 e.g., you could change the previous example so that the
DropDownList control automatically causes a postback.

 By doing so, you could eliminate the button completely
and instead do your message processing in the event
handler for the S l t dI d Ch d event
SelectedIndexChanged event.

Without AutoPostBack
70

Notice: label didn’t change
didn t

Notice: selection event not handled until the button
click triggered a postback

With AutoPostBack
71

Notice: label changed because list
selection triggered a postback

Notice: button click also triggered postback but
only button click event handler is executed.

AutoPostBack
72

<fieldset>
<legend>Sample Form ‐ Testing Autopostback</legend>
<p><label>Address: </label><br />
<asp:TextBox ID="txtAddress" runat="server" /></p>
<p><label>Country: </label><br />
<asp:DropDownList ID="drpCountry" runat="server" AutoPostBack="true"
onselectedindexchanged="drpCountry_SelectedIndexChanged">
<asp:ListItem>United States</asp:ListItem>
<asp:ListItem>Canada</asp:ListItem>
</asp:DropDownList></p>
<p><label>
<asp:Literal ID="litZipOrPostal" runat="server" Text="Zip: " />
</label> <br />
<asp:TextBox ID="txtZipOrPostal" runat="server" /></p>
<asp:Button ID "btnSubmit" runat "server" Text "Submit"
ID="btnSubmit" runat="server" Text="Submit"
onclick="btnSubmit_Click" />
</fieldset>
protected void Page_Load(object o, EventArgs e)
<asp:Label ID="labMessage" runat="server" />
{
labMessage.Text = "In page load<br/>";
}
protected void drpCountry_SelectedIndexChanged(object o, EventArgs e)
t t d id d C t S l t dI d Ch d( bj t E tA )
{
labMessage.Text += "In country select event handler<br/>";
if (drpCountry.SelectedValue == "Canada")
litZipOrPostal.Text = "Postal Code";
else if (drpCountry.SelectedValue == "United States")
litZipOrPostal.Text = "Zipcode";
Zipcode ;
}
protected void btnSubmit_Click(object sender, EventArgs e)
{
labMessage.Text += "In button event handler<br/>";
}

Visually Detecting Postback
y g
73

1

2 Browser will go blank at start of any new HTTP
GET or POST request (including a postback
request) and/or will be request delay.

When testing a web site locally, this can happen 3 Postback request finished rendering in browser.
too quickly to notice, but will be noticeable when
hosted on a real remote web server (especially a
busy one).

Visually Detecting Postback
y g
74

Normal postback request always incurs a delay
because it is a round trip
round-trip:
• request (across internet),
• execute, (on server),
• response (across internet),
• render in browser.

Using AJAX
g
75

 It is possible to asynchronously make a postback
request using ASP.NET’s AJAX abilities.
 This avoids the blank screen and wait of a full postback
p
request.
 Instead, the browser will make the request “in the
background”using asynchronous Javascript (AJAX).

76 ASP.NET
ASPNET AJAX
Another Di
A h Digression
i

ASP.NET AJAX
 ASP.NET AJAX adds Asynchronous JavaScript and
XML (AJAX) support to ASP.NET.
 ASP.NET AJAX was up until the fall of 2006 was
known by the code-known of Atlas.

ASP.NET AJAX
 AJAX is not a product.
 Rather it is the most common name given to a style of
web development that makes fuller use of Javascript
and the browser Document Object Model (DOM) in the
construction of web application user interfaces.

ASP.NET AJAX
 AJAX web applications also make use of all the
current browsers’ ability to asynchronously request
and receive information from the browser
independently of the usual page request/page
receive/page display cycle.
 Thisability to asynchronously communicate with the
server makes it possible to create pages that are more
responsive and l di
i d less disruptive.
ti

Normal web application client-server interaction

AJAX web application client-server interaction

ASP.NET AJAX Examples
p
Here client-side only (no communication
with server) Javascript is being used to
ih )J i i b i d
provide a richer user experience.

Here the browser is communicating asynchronously with
the server (the loading animation tells the user this) in
order to provide a list of relevant search terms.

Javascript is being used to make the request and
receive the d
h data b k in either XML or JSON format.
back h f

AJAX
 Asynchronous communication is typically achieved in
y yp y
Javascript using the XMLHttpRequest object (though
some sites use hidden IFrame elements instead).
 This bj t
Thi object was initially offered i I t
i iti ll ff d in Internet E l
t Explorer 5 as an
ActiveX component;
 FireFox, Opera, and Safari subsequently have added
native support for XMLHttpRequest.
 However, since Internet Explorer 5 and 6 XMLHttpRequest
support is via an ActiveX component, it is possible for the
pp p , p
user to disable it via browser settings.
 Internet Explorer 7, like the other browsers now supports
XMLHttpRequest natively
natively.

AJAX
 While richer AJAX web applications are a real
boon for the user, creating them can be a real
nightmare for the developer.
g p
 Javascript as a language lacks the kind of object-
oriented features developers expect.
 As well, Javascript can be quite difficult to debug.

 As a consequence, there has been a proliferation of
frameworks and toolkits to simplify the process of
f k d lk lf h f
developing AJAX applications.

Why AJAX Applications Are Good
y pp
 Fewer roundtrips
 Less bandwidth
 only need to transfer info/markup that needs updating
 Less work for the web server
 More responsive for the user

Why AJAX Applications Are Bad
y pp
 Accessibility problems
 Often don’t work very well with screen readers.
 Can be harder to develop
 Can be a nightmare to debug

AJAX at Work
87

Only these areas were
“updated” creating the
illusion of better
1 responsiveness

2 Notice: no obvious round-trip (though request +
execution + response did happen, it just happened
p pp , j pp
in the background asynchronously).

ASP.NET AJAX Coding
g
88

<form id="form1" runat="server"> Ensures appropriate
Javascript libraries are sent
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
to browser.
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate> Any postback requests within
<fieldset> this UpdatePanel will be done
<legend>Sample Form ‐ Testing Autopostback</legend>
asynchronously.
y y
<p><label>Address: </label><br />
<asp:TextBox ID="txtAddress" runat="server" /></p>
<p><label>Country: </label><br />
<asp:DropDownList ID="drpCountry" runat="server" AutoPostBack="true"
onselectedindexchanged="drpCountry_SelectedIndexChanged">
<asp:ListItem>United States</asp:ListItem>
p p
<asp:ListItem>Canada</asp:ListItem>
</asp:DropDownList></p>
<p><label><asp:Literal ID="litZipOrPostal" runat="server" Text="Zip: " /></label> <br />
<asp:TextBox ID="txtZipOrPostal" runat="server" /></p>
<asp:Button ID="btnSubmit" runat="server" Text="Submit"
onclick="btnSubmit_Click" />
</fieldset>
/fi ld t
<asp:Label ID="labMessage" runat="server" />
</ContentTemplate>
</asp:UpdatePanel>

</form>

89 ASP.NET B hi d h S
ASPNET Behind the Scenes
Warning: Advanced Stuff Ahead
W i Ad d S ff Ah d
(you may want to wait until later to cover this)

ASP.NET Behind the Scenes
90

 What happens when the browser requests an
pp q
ASP.NET web page?
 Quick Answer
 the visual elements of the page are parsed into a class,
 this class, along with its code is dynamically compiled
(into MSIL)
(i t MSIL),
 This MSIL is JIT compiled and then executed on the
server, ,
 Execution produces the HTML and Javascript that is then
sent to the browser.

ASP.NET 2.0 Compilation Process
p
91

Where is this stuff?
92

 The path for the generated class files created from
the web forms along with the temporary assemblies
is
 [.NET System Directory]Temporary ASP.NET Files[virtual
directory][x][y]
where x and y are randomly-generated names.
 For instance, the path for the assembly on my
development server was
C:WINDOWSMicrosoft.NETFrameworkv4.0.30319Temporary ASP.NET Fileschapter27229f9fd8d0746a9.

Parsed Class (created by ASP.NET from web form)
93

Page class
g
94

 All Web forms ultimately inherit from the Page class,
which is defined in the System.Web.UI namespace.

ASP.NET 2.0 Class Inheritance
95

Page class
g
96

 The Page class inherits from the TemplateControl class,
which in turn inherits from the Control class.
 As a result, the Page class provides a great deal of
functionality exposed as properties and methods
that you can make use of in your web forms.
y y
 Some of these properties are analogous to the
intrinsic global objects of ASP classic, such as Request,
Response, Session, and Server.

Application Lifecycle
pp y
97

 The page life cycle is just one of several processing
steps which occur as part of the larger ASP.NET life
cycle.
y

Application Lifecycle
pp y
98

Web II - 02 - How ASP.NET Works

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