chapter 6 - asp.net web form

8/9/2019 Chapter 6 - ASP.NET Web Form

1/42

ASP.NET Web Forms

Main Menu 1 of 42

ASP.NET Web Forms


2/42

ASP.NET Web Forms

Main Menu 2 of 42

Objective

At the end of this chapter, you will be able to

understand what are ASP.NET Web Forms, how

Visual Studio.NET creates these.

You will an understanding of how and why

Microsoft has separated the user interface resources

from the business logic.

You will also get in-depth knowledge of the PageClass, Page, the sequence of events and setting the

Page Directives.


3/42

ASP.NET Web Forms

Main Menu 3 of 42

What are Web Forms?

ASP.NET Frame work

Visual Studio ASP.NET Web Applications

Where Does Visual Studio Fit In?

Whats in Your Project?

Web Forms Code Model

Page Class

Scope


4/42

ASP.NET Web Forms

Main Menu 4 of 42

Location

Properties of Page class

Methods

Events of Page class

Web Forms page life cycle

Page_Init Event

Page_Load Event

Other Events

Page_Unload Event

Scope


5/42

ASP.NET Web Forms

Main Menu 5 of 42

ASP.NET Page directives

Page

Control

Import

Register

Assembly

OutputCache Implements

Reference

Scope


6/42

ASP.NET Web Forms

Main Menu 6 of 42

ASP.NET web forms are nothing but text files,

saved with an extension of.aspx.

The web forms can be created in the following three

ways:

Notepad

Front Page

VB.NET web Forms

What are Web Forms ?


7/42

ASP.NET Web Forms

Main Menu 7 of 42

Web Forms has the following features : -

Browser-independent applications.

Event-based programming model.

Abstract, intuitive, consistent object model.

State management.

Scalable server performance.

ASP.NET Frame Work


8/42

ASP.NET Web Forms

Main Menu 8 of 42

Visual Studio ASP.NET Web

Applications ASP.NET Web applications run on a Web server

configured with Microsoft IIS.

You do not need to learn working directly with IISor configuring it. It can all be programmed using

ASP.NET classes.

Visual Studio handles all the file management tasks

such as creating IIS applications when needed and

providing ways for you to even deploy your Web

applications to IIS.


9/42

ASP.NET Web Forms

Main Menu 9 of 42

The advantage of using Visual Studio is that it

provides tools that make web Application

development much faster, easier, universally

readable and much more robust. These tools include:

Visual designers

Code-aware editors

Integrated compilation and debugging

Project management

Where Does Visual Studio Fit In?


10/42

ASP.NET Web Forms

Main Menu 10 of 42

The ASP.NET Web Application project template

automatically adds the essential project references

and files to use as a starting point for your

application. When you create a Web project in Visual Studio,

Web Forms designer is opened.

The Web Forms designer is the design surface foryour pages.

Whats in Your Project ?


11/42

ASP.NET Web Forms

Main Menu 11 of 42

You can use the design view (which is open in the

image ) to design the lay out your page and its

elements, HTML view to view the raw HTML

generated for your page, and the code-behind viewto look at the code file associated with your page.



12/42

ASP.NET Web Forms

Main Menu 12 of 42

When you create a Web project, Visual Studio

constructs a Web application directory structure on

the target Web server that you have configured

(Your IIS in this case), And a project structure on your local computer.



13/42

ASP.NET Web Forms

Main Menu 13 of 42

Separation of user interface resources from business

logic:

Web Forms divide the Web applications into two pieces:

User Interface: . It is the visual part, which interacts with the user.

This part will be dealing with the user.

Business Logic:

User interface logic for the Web form consists of code that you

create to interact with the form in a separate file also known as

"code-behind" file.

Web Forms Code Model


14/42

ASP.NET Web Forms

Main Menu 14 of 42

When the web form page is compiled, ASP.NET

generates a new class and then compiles the new

class.

This new class is derived from the ASP.NET Pageclass, but is extended with controls, your code, and

the static HTML text in the. aspx file.

In ASP.NET entire Web Form is an executableprogram whose output is HTML.

Page Class


15/42

ASP.NET Web Forms

Main Menu 15 of 42

The page goes through a series of processing stagesanalogous with those of other componentsinitialize, process, and dispose.

The page class performs these stages each time thepage is called; that is, the page is initialized,processed, and disposed every time a call is made tothe server.

For efficiency the information required to recreatethe page is cached, but this is independent of itslifecycle.

Page Class


16/42

ASP.NET Web Forms

Main Menu 16 of 42

Page class Defines the properties, methods, and

events common to all pages that are processed on the

server by the Web Forms page framework.

Location


17/42

ASP.NET Web Forms

Main Menu 17 of 42

Examples of Page Class Properties:

Write the following code in the page_Load event

Response.Write(Page.Application)

Response.Write("
Is PostBack = " &Page.IsPostBack)

Properties of Page Class


18/42

ASP.NET Web Forms

Main Menu 18 of 42

The output would be:

Properties of Page Class

AS b


19/42

ASP.NET Web Forms

Main Menu 19 of 42

Write the following code in the Page_Load event to

see the absolute URL of your web form

Response.Write(Page.ResolveUrl

("WebForm1.aspx"))

Methods

ASP NET W b F


20/42

ASP.NET Web Forms

Main Menu 20 of 42

Output would be:

Methods

ASP NET W b F


21/42

ASP.NET Web Forms

Main Menu 21 of 42

With all these properties, methods and events Web

Forms offer great functionalities to the programmer.

As every web form ultimately gets compiled in toclass, which is a sub class of Page class, hence this

new compiled class can access all the methods of its

parent class.

Public Instance Events of Page

class

ASP NET W b F


22/42

ASP.NET Web Forms

Main Menu 22 of 42

Life cycle of any process consists of various stages

involved in its life.

The life cycle for a Web Forms page is, similar to

that of any Web process that runs on the server.

In Web Forms, most user actions such as clicking a

button result in a round trip.

For that reason, the events available in Web Formscontrols are limited.

Most controls expose a click event.

Web Forms Page Life Cycle

ASP NET W b F


23/42

ASP.NET Web Forms

Main Menu 23 of 42

Life cycle of a Web Form page can be divided in

three main events: -

Page_Init Event

Page_Load Event

Other Events

Page_Unload Event

Web Forms Page Life Cycle

ASP NET W b F


24/42

ASP.NET Web Forms

Main Menu 24 of 42

This is the first event in page life cycle. This event is

fired whenever the page is initialized.

Example:

Enter the following code in the page_init event

Response.write(
In Page init

event )

And this would be the first line on your web page.

Page_Init Event

ASP NET W b F


25/42

ASP.NET Web Forms

Main Menu 25 of 42

This is event is fired when the page is loaded.

Difference between init and loading event is that the

controls are fully loaded in the load event only.

Enter the following code in the Page_Load event

Response.Write("
In page load

Page Loaded at : " &

DateTime.Now) And this would be the second line on your web page.

Page_Load Event

ASP NET W b F


26/42

ASP.NET Web Forms

Main Menu 26 of 42

These are the events, which are fired after the

Page_Load event.

If the page was called in response to a form event,

the corresponding event-handling method in thepage is called during this stage.

Events like button_pressed;

mouse_clickedetc. can be put here.

Control Events

ASP NET Web Forms


27/42

ASP.NET Web Forms

Main Menu 27 of 42

This event is called, when the page has performed

all necessary actions and is ready to be discarded.

All the coding, necessary before cleaning up, is

placed here. Few of such tasks could be closing files,closing database connections, or discarding objects.

It is always better to close the connections, which

has been opened in your program.

Page_Unload Event

ASP NET Web Forms


28/42

ASP.NET Web Forms

Main Menu 28 of 42

ASP.NET supports few directives, which are used tospecify optional settings used by the page compilerwhen processing ASP.NET files.

These directive can be placed anywhere in the pagebut conventionally these are placed at the top of thefile.

Each directive can contain one or more

attribute/value pairs specific to that directive.Syntax of using directive as follows: -

ASP.NET Page Directives

ASP NET Web Forms


29/42

ASP.NET Web Forms

Main Menu 29 of 42

The @ Page directive defines page-specificattributes used by the ASP.NET page parser andcompiler.

You can only include one @Page directive per.aspx file.

To define multiple attributes, use a space-separatedlist, with no space around the equals sign, as inTRACE="True".

@Page

ASP NET Web Forms


30/42

ASP.NET Web Forms

Main Menu 30 of 42

The @ Control directive defines user control-specific attributes used by the ASP.NET pagecompiler.

This directive can only be used with user controls.

The @ Control directive supports the same attributes

as the @ Page directive, except the AspCompat andTrace attributes.

You can only include one @ Control directive per.ascx file.

@Control

ASP NET Web Forms


31/42

ASP.NET Web Forms

Main Menu 31 of 42

The @ Import directive explicitly imports anamespace into a page, making all classes andinterfaces of the imported namespace available tothe page.

The imported namespace can be either part of the.NET Framework class library or a user-definednamespace. Syntax is as follows: -

The @ Import directive cannot have more than one

namespaceattribute.

@Import

ASP NET Web Forms


32/42

ASP.NET Web Forms

Main Menu 32 of 42

The @Register directive associates aliases with

namespaces and class names for concise notation in

custom server control syntax.

When a new namespace is added to a page you haveto specify to the compiler few things about the

control.

With this information compiler can recognize the

control.

@Register

ASP NET Web Forms


33/42

ASP.NET Web Forms

Main Menu 33 of 42

There are two ways to use this tag: -

@Register

ASP NET Web Forms


34/42

ASP.NET Web Forms

Main Menu 34 of 42

The @Assembly directive declaratively links anassembly to the current page, making all of theassembly's classes and interfaces available for use onthe page.

You can also use this directive to register assembliesin the configuration file to link assemblies across theentire application.

It is not necessary to include the path of an assembly

in a @ Assembly directive.

@Assembly

ASP NET Web Forms


35/42

ASP.NET Web Forms

Main Menu 35 of 42

This directive is used to control the caching of a

page on the server.

The @OutputCache directive declaratively controls

the output caching policies of a page.

@OutputCache

ASP NET Web Forms


36/42

ASP.NET Web Forms

Main Menu 36 of 42

The @implements directive allows you to

implement a .NET interface in your page.

When an interface is implemented the page supports

the defined properties, events and methods of thespecified interface.

Using the following syntax this directive is used

@Implements

ASP NET Web Forms


37/42

ASP.NET Web Forms

Main Menu 37 of 42

It declaratively indicates that another user control or

page source file should be dynamically compiled and

linked against the current page.

Attributes

Page

Control

@Reference

ASP NET Web Forms


38/42

ASP.NET Web Forms

Main Menu 38 of 42

Key points covered in this chapter are:

Web forms are used to share information between browser

and server.

Web forms are text files only, saved with an extension ofaspx.

Visual Studio.NET provides an easy to use GUI for

developing web applications.

There is no need to create a virtual directory every timewe create a web application in Visual Studio.NET

Summary

ASP.NET Web Forms


39/42

ASP.NET Web Forms

Main Menu 39 of 42

Visual studio provides different views to write different

types of codes eg. HTML view, Code View, design view

Visual studio generates a number of files with different

functionalities in the web project.

Web forms Code Model provides separation of the html

code from programming logic.

Page is represented as a class in .NET framework.

Page has its own class hierarchy, properties, methods andevents.

Web forms Page Life Cycle is based on events.

Summary

ASP.NET Web Forms


40/42

ASP.NET Web Forms

Main Menu 40 of 42

Page_Init Event is the first event fired as soon as the page

is loaded.

Other Events are events fired by the program depending

on the page. These events are defined by the developer

e.g. button click event.

Page_Unload Event is the last event to write the clean up

code.

ASP.NET Page directives are used to declare various

directives on the page namely Page, Control, Import,

Register, Assembly and OutputCache. These give our web

page a default behavior.

Summary

ASP.NET Web Forms


41/42

ASP.NET Web Forms

Main Menu 41 of 42

Fill in the blanks:

1. ______________event is called, when the page has

performed all necessary actions and is ready to be

discarded.2. _____________ is a WYSIWYG editing tool for

designing and programming our Web Forms.

3. ASP.NET web forms are nothing but text files, saved

with an extension of ________.4. Code behind file has a ___________ extension.

Self Assessment

ASP.NET Web Forms


42/42

ASP.NET Web Forms

State True/False :

1. Web forms can be created using visual studio.net only.

2. Web forms are used to share information between

browser and server.3. Web forms are windows based forms.

4. Page directives are used to control information with in

the aspx page.

Self Assessment

chapter 6 - asp.net web form

Documents