Anatomy of an ASP.NET Pages

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Anatomy of an ASP.NET Pages
OutlineASP.NET Life CycleInternet Information
Services (IIS 5.0)A Simple PageIntroducing
In-Line ScriptCode-Behind
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A Simple Page

• ASP.NET can be developed with a simple text
  editor or by using Visual Studio .NET
• A Simple Page
• .aspx pages are parsed by aspnet_wp.exe into HTML
  pages

lthtmlgtltbodygtHello Worldlt/bodygtlt/htmlgt
lthtmlgtltbodygtHello Worldlt/bodygtlt/htmlgt
Internet
aspnet_wp.exe
HelloWord.aspx
Result on the client side
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A Simple Page

• Adding a Web Control

Internet
HelloWorld.aspx
aspnet_wp.exe
Html page on the client side
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Microsoft Internet Information Services (IIS) 5.0

• Can be started by double clicking on
• Control Panel -gt Performance and maintenance -gt
  Administrative Tools -gt Internet Information
  Services
• Or type inetmgr on the Start menus Run command
  prompt.

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Microsoft Internet Information Services (IIS) 5.0
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Virtual Directory
C\Inetpub\wwwroot\index.aspx
http//localhost/index.aspx
C\Inetpub\wwwroot\myweb/index.aspx
http//localhost/myweb/index.aspx
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Virtual Directory
Alias
Directory
New virtual directory
CIS340Web
D\WebFiles\
D\WebFiles\home.aspx
http//localhost/CIS340Web/home.aspx
D\WebFiles\root\home.aspx
http//localhost/CIS340Web/root/home.aspx
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Microsoft Internet Information Services (IIS) 5.0
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Microsoft Internet Information Services (IIS) 5.0
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Microsoft Internet Information Services (IIS) 5.0
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Microsoft Internet Information Services (IIS) 5.0
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Introducing In-Line Script

• lthtmlgt
• ltheadgt
• lt/headgt
• ltbodygt
• ltform runatservergt
• ltaspLabel idlblHelloWorld text"Hello World"
  runatserver /gt
• ltbrgt
• ltaspButton onclickClickedIt text"Submit"
  runatServer /gt
• lt/formgt
• lt/bodygt
• ltscript LanguageC runatservergt
• void ClickedIt(object sender, System.EventArgs
  e)
• lblHelloWorld.Text ".NET Rules!"
• lt/scriptgt
• lt/htmlgt

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Introducing In-Line Script
HelloWorld31.txt
HelloWorld32.txt
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Advantages of Code-Behind

• Clean separation of HTML and code
• Code in any Visual Studio language (C, VB, C,
  J)
• Easier reuse
• Simpler maintenance
• Deployment without source code
• Separate the script from the interface
• Interface and Logic can be done in parallel
• Compile errors are found without the need to
  request the page
• Protect your code.
• Promote code reuse

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Code-Behind

• Steps to use code-behind approach
• Include header in the aspx file that refers to
  the code-behind file
• Code-behind file shall be compiled into class
  library (.dll file) and inserted in the bin
  directory

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Code-Behind HelloWorld.aspx
Page directive

• lt_at_ Page language"c" Codebehind"HelloWorld.aspx
  .cs" Inherits"MyProject.HelloWorld" gt
• ltHTMLgt
• ltHEADgt
• lttitlegtCode Behindlt/titlegt
• lt/HEADgt
• ltbodygt
• ltform id"Form1" method"post" runat"server"gt
• ltaspLabel id"lblHelloWorld" runat"server"gtHell
  o Worldlt/aspLabelgtltbrgt
• ltaspButton id"Button1" runat"server"
  Text"Submit"gtlt/aspButtongt
• lt/formgt
• lt/bodygt
• lt/HTMLgt

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Code BehindHelloWorld.aspx.cs

• namespace MyProject
• public class HelloWorld System.Web.UI.Page
• protected System.Web.UI.WebControls.Label
  lblHelloWorld
• protected System.Web.UI.WebControls.Button
  Button1
• private void Page_Load(object sender,
  System.EventArgs e)
• // Put user code to initialize the page here
• private void ClickedIt(object sender,
  System.EventArgs e)
• lblHelloWorld.Text ".NET Rules!"

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Code-Behind

• Page Class
• Inherited from System.UI.Page
• Provide the base functionality that requires the
  ASP.NET to run

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Code-BehindHelloWorld.aspx

• lt_at_ Page language"c" Codebehind"HelloWorld.aspx
  .cs" Inherits"MyProject.HelloWorld" gt
• Language Defines the programming language
• Codebehind Set the filename of the code-behind
  file
• Inherits Must be inherited from the Page class

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Special Page Class Events

• private void Page_Initfired when the page is
  first instantiated
• First event fired in the page life cycle
• All the controls for the page are created
• Not used in your program, it is used by the VS to
  insert auto generated code
• private void Page_Load fired after the page's
  controls are initialized, but before the page is
  rendered.
• Fired after Page_Init
• Page view state is available
• Perfect place for run-time initialization
• Visual Studio generates a stub for this event.
• private void Page_Unload
• Fired when the page is unloaded from memory
• Good place to take care of any clean-up for the
  page

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ASP.NET File Types

• .aspx Web forms
• .ascx Web forms user controls
• .asmx Web services
• .vb Visual Basic
• .cs C
• Global.asax Defines application- and
  session-variables
• Web.config Configuration settings

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Visual Studio Files

• Global.asax
• Used to handle special ASP.NET application such
  as Application_Start and Session_Start
• Web.Config
• XML file used for making overall application
  settings such as security and session state
• .dosco
• Used to advertise any web services that our
  website offer.
• .aspx
• ASP.NET file that defines the web page interface
• .aspx.cs
• C file that defines the business logic in the
  web page

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Maintaining State

• Input Controls
• TextBox, ListBox, CheckBox, etc.
• Automatically remember their state via
  "postback data sent in the HTTP header
• Display Controls
• Label, DataGrid, etc. (i.e. controls not set by
  user)
• Automatically remember their state via
  "viewstate", a hidden control. State is
  automatically serialized into and out of the
  viewstate. This behavior can be turned off if
  desired.

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Maintaining State

• Cookies
• Small chunks of text that are sent back and
  forth between the browser and the server.
• Cookies have names and values.
• Session cookies are valid only until the
  browser closes.
• Persistent cookies have a specified lifetime
  independent of the browser's lifetime.
• The page's Request and Response objects have
  cookie collections.

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Saving State on the Server

• Application
• The same dataset is used by all sessions
• Session
• Users need to preserve their random number
  generators and how their last stories started

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Application State

• Values are stored in a hashtable available to all
  code in the application
• A synchronization mechanism enables developers to
  coordinate concurrent access to state information
• Other applications cannot access or modify values

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Application State

• There is a memory impact of storing application
  state.
• Synchronization is important if simultaneous
  access is a possibility.
• Locking resources can force other processes to
  operate in a serial manner.
• Application state does not survive the tear-down
  of the hosting process.
• Application state is not shared across a web farm
  (multiple servers) or web garden (multiple
  processors on a single server).

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Session State

• Very importantshopping carts, data scrolling,
  etc.
• Can be released after a timeout period
• Can survive IIS or worker process restarts. State
  does not have to be not stored in the worker
  process.
• Scalableworks with web farms and web gardens
• Must work with browsers that reject cookies
• Good throughput required

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Session State

• In-process mode
• State is stored in the worker process and lost if
  the process is recycled
• The advantage is speed
• Out-of-process mode
• State server mode uses a Windows Service
  Aspnet_state.exe
• State is memory-based.

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Page-Level Events

• In-process mode
• State is stored in the worker process and lost if
  the process is recycled
• The advantage is speed
• Out-of-process mode
• State server mode uses a Windows Service
  Aspnet_state.exe State is memory-based.
• SQL Server mode persists the state information to
  a SQL server. Servers could be clustered to
  replicate data.
• The choice is made in configuration files

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Using the Global.asax file

• Contains event handlers for responding to
  application- and session-level events
• Resides in the root directory of the application
• Optionalno handlers need be defined
• Generated automatically by Visual Studio
• Can use code-behind in Global.asax.cs

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Using the Global.asax file

• Contains event handlers for responding to
  application- and session-level events
• Resides in the root directory of the application
• Optionalno handlers need be defined
• Generated automatically by Visual Studio
• Can use code-behind in Global.asax.cs
• protected void Application_Start(Object sender,
  EventArgs e)

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Using the Global.asax file

• Contains code for responding to application- and
  session-level events
• Resides in the root directory of the application
• Optionalno handlers need be defined
• Generated automatically by Visual Studio
• Can use code-behind in Global.asax.cs
• protected void Application_Start(Object sender,
  EventArgs e)
• Session_Start
• Application_End
• Session_End
• Application_Error

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Postback

• private void Page_Load(object sender,
  System.EventArgs e)
• //Place any code that needs to be executed on
  every request here. This
• //could be things such as setting up a database
  connection that will
• //be used throughout the processing of the page.
• if(!IsPostBack)
• //Place any code that needs to be executed only
  on first request
• //here. This would include things such as
  retrieving static data
• //from the database and populating drop-down
  lists or tables with
• //this data.
• else
• //Place any code that needs to execute only on a
  postback here.
• //This might include code that checks for some
  kind of user input
• //that wouldnt be available when the page Is
  first requested.

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Performance considerations

• Disable session state when you are not using it
• Choose the session state provider carefully
• Avoid unnecessary round trips to the server
  (e.g., could validate input on the client)
• Use IsPostBack to avoid unnecessary processing on
  a round trip
• Save server control view state only when
  necessary
• Don't rely on exceptions as a way to control
  program flow.
• Use SQL Server DataReader for fast forward-only
  data access
• See ASP.NET Caching for ways to cache page output
  or data