ASP.net Session 01

7/30/2019 ASP.net Session 01

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Slide 1 of 39Ver. 1.0

Developing Web Applications Using ASP.NET

With the increased use of the Internet and advances in

information technology, application developers need to

quickly create applications that are accessible over the Web

or a corporate intranet. The applications should also be

efficient and effective.

ASP.NET provides developers with various time saving and

code saving features. One of its key design goals is to make

programming easier and quicker by reducing the amount of

code. In addition, it contains several new server controls,

which eliminate the need for writing voluminous code.

Rationale


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In this session, you will learn to:

Identify the basics of Web development

Explore ASP.NET

Develop ASP.NET applications

Objectives


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Web applications are programs that can be executed on a

Web server and accessed from a Web browser.

Web applications enable organizations to share and access

information on the Internet and corporate intranets.

A Web application consists of the following types of Webpages:

Static Web page

Dynamic Web page

An application that consists of dynamic Web pages is a

dynamic Web application.A Web application can be made dynamic by using

server-side and client-side scripts.

Introducing Web Development


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Server-side scripting provides users with dynamic content

that is based on the information stored at a remote location,

such as a back-end database.

Server-side scripting includes code written in server-side

scripting languages, such as:Active Server Pages (ASP).

Java Server Pages (JSP).

A server-side script is executed on a Web server.

Server-Side Scripting


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The following figure shows the working of server-side

scripts.

Server-Side Scripting (Contd.)


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Client-side scripting:

Enables you to develop Web pages that can dynamically

respond to user input without having to interact with a Web

server.

Provides dynamic content.

Helps reduce network traffic because it does not need to

interact with a Web server to provide dynamic response to user

input.

Speeds up the response time of a Web application.

Scripting languages such as VBScript and JavaScript are

used to write client-side scripts.

Client-Side Scripting


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The following figure shows the working of client-side scripts.

Client-Side Scripting (Contd.)




Limitations of client-side scripting:

Browser support: Client-side scripting is not supported equally

by all browsers and operating systems.

Isolation: Client-side scripts cannot access server-side

resources.

Security: Client-side scripts are visible to the end users.

Therefore, they can be tampered by malicious users.

Thin clients: Web-enabled devices such as mobile phones,

palmtop computers, and Personal Digital Assistants (PDAs) do

not support client-side scripting such as JavaScript or

VBScript.

Client-Side Scripting (Contd.)




ASP.NET is a server-side technology that enables

programmers to create dynamic Web applications.

ASP.NET has a number of advanced features such as

simplicity, security, and scalability that help you develop

robust Web applications.The various advanced features of ASP.NET are based on

the .NET Framework.

Exploring ASP.NET


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The following figure displays the elements of an ASP.NET

application and how the elements fit in the broader context

of the .NET Framework.

ASP.NET in the .NET Framework


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The following figure depicts how a Web server processes a

request for an ASP.NET file.

Working of an ASP.NET Application


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An ASP.NET application can be created by using any text

editor. However, this is a very time-consuming process.

In addition, this process increases the possibility of inducing

errors that could otherwise be avoided by using a design

tool.

A design and productivity tool, such as Visual Studio,

provides various features that enable the developers to

quickly create robust ASP.NET applications.

Developing ASP.NET Applications


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Some of the features of Visual Studio IDE are:

Integrated error checking

The Web form designer

An integrated Web server

Developer productivity enhancementsComplete extensibility

Developing ASP.NET Applications (Contd.)


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Website Types

You can use Visual Studio 2008 to create the following

types of websites:

File-system websites

Local Internet Information Services (IIS) websites

Remote IIS websitesFTP sites

Let us see how to create an ASP.NET website

Let us see how to open an existing ASP.NET website


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The following table lists some specialized directories that an

ASP.NET application uses.

Anatomy of an ASP.NET Application

Directory Descript ion

Bin Stores all the compiled .NET components (DLLs) that an ASP. Web

application uses.

App_Code Stores source code files that are dynamically compiled to be used in theWeb application.

App_Browsers Stores browser definition files. Browser definition files are XML files that

define a browser with its properties, capabilities, and features.

App_GlobalResources Stores global resources that are accessible to every page in the Web

application.

App_LocalResources Stores .resx files that are accessible to a specific page only.

App_WebReferences Stores references to Web services that are used by the Web application.

App_Data Stores data such as database files and XML files that are used by the

application.

App_Themes Stores the themes that are used in the Web application.


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The following table lists some important file types that an

ASP.NET Web applications can include.

Anatomy of an ASP.NET Application (Contd.)

File Name Descript ion

Ends with .aspx These are ASP.NET Web pages that contain the user interface and, optionally, the

underlying application code. Users request or navigate directly to one of these pages

to start a Web application.

Ends with .ascx These are ASP.NET user controls. These controls are similar to Web pages, exceptthat the user cannot access these files directly. Instead, they must be hosted inside

an ASP.NET Web page. User controls allow you to develop a small piece of user

interface and reuse it in as many Web forms as you want without repeating code.

Ends with

.asmx

These are ASP.NET Web services. Web services are collections of methods that can

be called over the Internet. Web services work differently than Web pages. However,

they still share the same application resources, configuration settings, and memory.

web.config This is the XML-based configuration file for ASP.NET applications. It includes

settings for customizing features such as security, state management, and memorymanagement.

Global.asax This is the global application file. You can use this file to define global variables

(variables that can be accessed from any Web page in the Web application).

Ends with .cs These are code-behind files that contain C# code. These files allow you to separate

the application logic from the user interface of a Web page.

Ends with .ashx These are default HTTP handlers for all Web handlers that do not have a userinterface and that include the @ WebHandler directive.


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Configuration files used in ASP.NET Web applications:

ASP.NET uses a hierarchy of configuration files to keep

application configuration settings separate from the application

code.

A configuration file is an XML file that contains configuration

settings for an application and has a .config extension.

Benefits of a configuration file:

It provides control and flexibility over the way you run

applications.

It eliminates the need to recompile the application every time a

setting changes.

It controls access to protected resources, and the location of

remote applications and objects by defining configuration settings.



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The following table lists the levels, the corresponding

configuration files, and their description.


Level File Name Descript io n

Server Settings Machine.config Present at the root of the configuration hierarchy. It

defines global configuration settings for all . Framework

applications.

Root Web Settings Web.config Present in the same directory as machine.config. Itdefines configuration settings for all ASP. applications.

Website settings

(optional)

Web.config Present in the root directory of each IIS website. It

contains settings that are specific to the website.

Application root

Settings (optional)

Web.config Present in the root directory of each application. It

contains settings that are specific to the application.

Application

subfolder (optional)

Web.config Present in a subfolder of the application root. It contains

settings for specific section of a Web application.Server Settings Machine.config Present at the root of the configuration hierarchy. It

defines global configuration settings for all . Framework

applications.


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A Web page is made up of the following two components:

The visual portion: It refers to the static HTML and ASP.NET

server controls that define the layout of a Web page.

The programming logic: It refers to the code that is required to

interact with the Web page.

ASP.NET provides the following two models for managing

the visual elements and code:

Single-file page model

Code-behind page model

ASP.NET Web Page Code Model


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The single-file page model:

In the single-file page model, HTML markup of the page and its

programming code are in the same physical .aspx file.

The programming code is contained in a block that

specifies the attribute runat=server.

The single-file page model provides the following advantages:

In pages with less code, keeping the programming code and the

HTML markup in a single file proves to be very convenient while

studying the file.

Pages written by using the single-file model are slightly easier to

deploy or to send to another programmer because there is only

one file.

A single-file page is easier to rename because there is no

dependency between files.

Managing files in a source code control system is slightly easier

because the page is self-contained in a single file.

ASP.NET Web Page Code Model (Contd.)


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The code-behind page model:

In the code-behind page model, HTML markup is kept in one

file with extension .aspx and the programming code in another

file with extension .cs or .vb.

The code file contains a partial class, which indicates that the

class contains only some of the total code that makes up thefull class for the page.

The code-behind model provides the following advantages:

It allows a developer to separate the UI display from the UI

processing, thereby enabling the programmer to reuse the

programming logic.

It enables a developer to quickly debug the code because the

code is not clubbed with the UI.

It enables developers to quickly create a Web application by

separating the design and development functions.

ASP.NET Web Page Code Model (Contd.)

Let us see how to add a new Web form to an ASP.NET website


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All Web forms are instances of the ASP.NET Page class,

which is defined in the System.Web.UI namespace.

The Page class inherits the TemplateControl class,

which, in turn, inherits the Control class.

ASP.NET uses an event-driven model of programming,which defines a sequence of events that are raised during

the lifecycle of a Web page.

The Page Class


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The following table lists some of the page events:

The Page Class (Contd.)

Event Descript ion

Init It is the first event that occurs when the server executes

an ASP.NET page. It occurs only once in the entire

lifecycle of an ASP.NET page.

Load It is fired after the Init event, when the page is requested

for the first time and whenever the page is reloaded.

This event can be used to initialize the variables and the

state of the controls that are used in the page.

Unload It represents the last event that occurs in the lifecycle of

an ASP.NET page. This event is used to perform final

cleanup work, such as the closing of open database

connections, discarding objects, or closing files.


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ASP.NET provides the following built-in objects:

Application

Request

Response

Server

Session

HttpContext

The built-in objects are made available to the Page object,

which is an instance of the System.Web.UI.Page class

from which all ASP.NET pages are inherited.

Intrinsic Objects of ASP.NET


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The Application object:

Provides a reference to an object of theHttpApplicationState class.

Is used to store information that is defined for the entire Web

application.

Has the following properties:

Count: It returns the number of objects in the

HttpApplicationState collection.

Item: It provides access to an object in the HttpApplicationState

collection.

Provides the following methods:public void Lock(): It blocks the access to an

Application variable or object.

public void UnLock(): It releases the lock procured on an

Application variable or object.

Intrinsic Objects of ASP.NET (Contd.)


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The Request object:

Provides a reference to an object of the HttpRequest class.

Enables ASP.NET applications to access information sent by

the client during a Web request.

Provides the following method:

byte[] BinaryRead(int): Helps retrieve the data sent to the

server from the client as part of a post request and stores it in an

array.



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The following table describes some of the properties of theRequest object.


Proper ty Descr ipt ion

ApplicationPath Returns the application root path of ASP.NET on the

server. This is a read-only property.

Url Returns a object, which will contain the completeaddress of the requested page. This is a read-only

property.

UserHostAddress Returns the IP host address of the requesting client.

UserLanguage Returns a sorted string array containing the language

preferences of the client.

Browser Returns the HttpBrowserCapabilities object, which

contains information about the browser capability of the

client.

Cookies Returns the HttpCookieCollection object, which provides

access to the cookie variables of the client.

QueryString Provides access to the parameters passed from the

client to the server along with a request.


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The Response object:

Provides a reference to an object of the HttpResponse class.

Enables ASP.NET applications to send information to the

client.

The following table describes some of the properties of theResponse object.



Buffer Sets the buffer feature of the Response object.

Cache Provides access to the caching policy, such as the

expiration time and privacy settings of the Web page.

ContentType Sets or gets the type of data that is sent to the clientthrough the Response object.

Cookies Sets a cookie to the client browser.

IsClientConnect

edReturns a Boolean value indicating whether the client is

connected or disconnected.


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The following table describes some of the methods of theResponse object.


Method Descr ipt ion

public void Clear() Clears the content in the buffer of the Response

object.

public void Close() Closes the connection to the client.public void End() Sends the buffered data to the client and closes the

connection to the client. The End() method will raise

an Application_EndRequest event.

public void Flush() Sends the data in the buffer to the client but does not

close the connection to the client.

public void Redirect(string) Redirects the new URL specified in the string

parameter to the client.

public void Write(string) Writes a string on the form. It is an overloadedmethod.

Let us see how to display a message on a Web page


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The Server object:

Provides a reference to an object of the HttpServerUtility

class.

Provides methods that can be used to access the methods and

properties of the Web server.


MachineName: It returns the name of the server machine.

ScriptTimeout: It helps get and set the request timeout in

seconds for the Web server.



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The following table describes some of the methods of the

Server object.


Method Descr ipt ion

public void ClearError() Clears the last error that has occurred on the server.

public object

CreateObject(String)Creates the server instance of a COM object.

public Exception

GetLastError()Returns an Exception object, which represents the last error that

occurred on the server.

public string

MapPath(string path)Returns the physical file path on the Web server that corresponds

to the specified virtual path.

public void

Transfer(string)Terminates the processing of the current page and loads the page

specified in the string format.


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The Session object:

Provides a reference to an object of the HttpSessionState

class.

Enables ASP.NET applications to keep the state of the

application as modified or changed by a client.

Provides access to the session wide cache, which can be used

to store information pertaining to the client.


Count: It returns the number of items in the session-state

collection.

SessionID: It returns the unique session ID assigned for asession.

Timeout: It enables to get and set the period in minutes that is

allowed between requests by the client before the session-state

provider terminates the session.



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Provides the following methods:

public void Add(string name, object value): Adds a

new item to the session-state collection.

public void Clear(): Clears all the values stored in the

session-state collection.

public void Remove(string name): Deletes an item from

the session-state collection.



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A new HttpContext object is created for every request

sent to an ASP.NET application.

The object is created at the beginning of a request and

destroyed when the request is completed.

The HttpContext object holds current request-specific

information such as Request, Response, Server, and

Session.


l i b li i i S


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The following table describes some of the properties of theHttpContext object.



AllErrors Gets an array of errors that are accumulated while processing

an HTTP request.

ApplicationInstance Gets or sets the HttpApplication object for the current HTTP

request.

Timestamp Gets the initial timestamp of the current HTTP request.

Users Gets or sets security information for the current HTTP request.

D l i W b A li ti U i ASP NET


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The following table describes some of the methods of theHttpContext object.


Method Descript ion

public void

AddError(Exception

errorInfo)

Adds an exception to the exception collection for the

current HTTP request.

public void ClearError() Clears all errors for the current HTTP request.

public object

GetConfig(string name)Returns requested configuration information for the

current HTTP request.



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In this session, you learned that:

Web pages can be of the following types:

Static Web page

Dynamic Web page

Server-side scripting provides users with dynamic content that

is based on the information stored at a remote location.

Client-side scripting enables you to develop Web pages that

can dynamically respond to user input without having to

interact with a Web server.

An ASP.NET application has the following elements:

Web Form pagesConfiguration files

XML Web service files

Summary



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ASP.NET has the following advanced features that help

develop robust Web applications:

Compiled code

Enriched tool support

Power and flexibility

SimplicityManageability

Scalability

Security

Extensibility

A Web form is made up of the following two components:

The visual portion

The programming logic

Summary (Contd.)



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ASP.NET provides two models for managing the visual

elements and code:

Single-file page model

Code-behind page model

ASP.NET provides the following built-in objects:

Application

Request

Response

Server

Session

HttpContext

Summary (Contd.)

ASP.net Session 01

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