ASP.NET Lecture 2

ASP.NET 4.0
Julie Iskander
MSC. Communication and Electronics

Course Outlines
 User Controls
 Validation Controls
 State Management

User Controls
“Always DRY”

User Controls (.ascx)
 A small section of page that can
include static HTML code, web server
controls.
 No <html>,<head>,<body>,<form>
tag
 Can be reused in multiple pages
 Can have properties and events
 Have same Page events, and same
Page properties
Session, Application,……,etc

User Control
 Step:
1. Create a .acsx file, add your controls
2. Write your code-behind logic
3. On your .aspx
a. Register the user control
b. Add it to the design

Convert from an HTML to an aspx page

Validation Controls
 Validates using client-side JavaScript
first, if valid posts back and validates
using server-side code.
 Must be bound to an input control
 CauseValidation property of controls
 Inherits from BaseValidator Class
(System.Web.UI.WebControls)

Validation Group (BONUS
Question)
 What if I added a new button with no
validation group?
 How to make sure a control is always
validated, regardless of the validation
group of the clicked button?
1- The button will validate controls with no validation
group only, if none is found the page is postback as valid

2- Create multiple validators for the control, one for each
validation group and one with no validation group

State Management
“The art of retaining
information between
requests”

To Windows
Form
developers, ASP.
NET seems like
continuous
running
applications!!!

A Clever ILLUSION

State Management
 Solution to stateless nature of HTTP
 To persist information between
requests.
 Store information over the lifetime of
the application
 Methods used
◦ Cross-Page Posting
◦ View state
◦ Query String
◦ Cookies
◦ Session State

ViewState
 Uses a hidden field
 Property of Page object, a dictionary
collection of name/value pairs
 Store information for multiple postback
within same page.
 Stores serializable objects only

ViewState Collection
 To save value
◦ this.ViewState[“ButtonClicked”]=1;
 To retrieve value
◦ int count =
(int)this.ViewState[“ButtonClicked”];

ViewState
 To use ViewState to retain member
variables. It is recommended to
◦ Save values in Page.PreRender
◦ Retrieve values in Page.Load
 Preserves the illusions of
continous application  cost??
 Another limitation  bound to one
specific page

Cross-Page Posting
 To transfer information from one
page to another using postback
mechanism
 Can lead you to create pages that
are tightly coupled to one another
and difficult to enhance and debug.
 The page will be posted with all
control values, even the hidden
viewstate values.

Page2

 In an IButtonControl  Access Page1 through
◦ PostBackUrl Property = “url PreviousPage Property
of page2”

Cross-Page Posting

Query String
 Is the portion of the URL after the question mark.
 Limitations:
◦ Strings, which must contain URL-legal characters
ONLY.
◦ Information is clearly visible .
◦ Can be modified by the user.
◦ Many browsers impose a limit on the length of a URL
(usually from 1 to 2 KB).
 Must be placed in the URL by you, using a
special HyperLink control, or you can use a
Response.Redirect()
◦ “MyPage.aspx?ID=3”
 To retrieve the values sent use QueryString
dictionary collection in the Request object,
◦ string ID = Request.QueryString["ID"];

Cookies
 Small files that are created in the web
browser’s memory or the clients hard
drive.
 Stores only strings.
 Accessible and readable
 Can be disabled in the browser.
 System.Net
 If no expiry date, the cookie is not
permenant.

Cookies
 Creating cookies and storing
information

Cookies
 Retrieving information from cookies

Session State
 User-specific
 Heavyweight state management method
 Support any type of objects
 Stored in the server memory in a dictionary
collection of name/value pair
 Instance of
System.Web.SessionState.HttpSessionState
class
 Adv.  never stored on client (Secure)
global over the entire application
 Unique SessionID for each user stored
◦ Using Cookies
◦ Using modified URLs
◦ Only part of the session sent to the client

Session State
 Session is lost when:
1. Close or restart browser
2. Use a different browser
3. Timeout due to inactivity
4. Call Session.Abandon();
 Session.Timeout  default 20
minutes
 Disadvantages
 Information is stored in the server memory
 Affect performance with increased usage

SQL Server Data Store for
SessionState
 Slowest SessionState storage
 Command to create Database Store

 Configure the web.config to use it

Application State
 Application object 
 Instance of System.Web.HttpApplicationState
class
 Store global objects that any client can
access, Stored in a dictionary of
name/value pairs
 Never timeout, unless the application
restarts
 Support any type of objects
 Retains information on the server.

ASP.NET
Application and
Global Events

Application Events
 Global.asax
◦ event handling global events events of
Application class.
◦ Can access all properties and methods of
Application object
◦ No HTML or ASP.NET tags.
◦ ONE AND ONLY ONE for each
application

Application Events
 PerRequest Events
◦ Application_BeginRequest()
◦ Application_EndRequest()
 PerSession Events
◦ Session_Start()
◦ Session_End()
 Special Events
◦ Application_Start()
◦ Application_End()
◦ Application_Error()

ASP.NET Configuration
 XML-based files
 Machine level
◦ machine.config
 [windows]Microsoft.NetFramework[Version]C
onfig
◦ Root web.config
 All applications inherit these
configurations

ASP.NET Configuration
 Per Application
◦ web.config
 In root application directory
◦ web.config in subdirectories

Reading Assignment #2
 Read ASP.NET Application Life Cycle
Overview for IIS 7.0
http://msdn.microsoft.com/en-
us/library/bb470252.aspx#GlobalAsax
 Custom Validators
 Rich Controls
◦ Calendars
◦ Sitemaps
◦ menus

Report #2
 Show a simple example of creating
and retrieving cookies in javascript.
 How can you load a User Control in
code?

Lab #2
 Add validations to the registration
form, Name(Required) and Age(between 18
and 120) at least.
 Add site map to the site (Self Study)
 In book.aspx,
◦ Create a UserControl (DateTimeControl.aspx) to
display the current date and time on the top-right
of the page. It must be refreshed every second
without postback.
◦ The checked books are added to the Shopping
Cart when checkout is pressed the chosen books
are displayed in a new checkout.aspx page .
◦ Create a user control to count number of visitors
and add it to the footer of all pages

Lab Hints
 Add events to dynamic controls
 Cast the object sender of the event to
the wanted control
 Use Javascript and/or jQuery for the user
control

 Try Trace=true in Page directive, to help
in debugging

Bonus
 In book.aspx
◦ When next and back is clicked the
previously checked books must stay
checked so as the user can know what he
already chose.

REFERENCES

 [1] Beginning ASP.NET 4 In C# 2010, Matthew
Macdonald, Apress
 [2] Web Application Architecture
Principles, Protocols And Practices, Leon Shklar
And Richard Rosen, Wiley
 [3] Professional AS P.NE T 4 In C# And VB, Bill
Evjen, Scott Hanselman And Devin Rader, Wiley
 [4] Pro ASP.NET In C# 2010, Fourth
Edition,matthew Macdonald, Adam Freeman, And
Mario Szpuszta, Apress

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