State Management in ASP.NET

ASP.NET
State management
1Shyam N. Chawda 9374928879

Welcome my dear students2
Shyam N. Chawda 9374928879

IsPostBack Property
Page class’s property , which you can use to detect whether the
page has already been post back to server.
True/False
True – Yes 2nd time
For View Effects
Take Dropdown and Add items in the form load
Take Button
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What is State management?
HTTP protocol is a stateless protocol.
Web server does not have any idea about the
requests from where they coming
On each request web pages are created and
destroyed.
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A new instance of the Web page class is created
each time the page is posted to the server.
All information associated with the page and the
controls on the page would be lost with each
round trip.
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So, how do we make web pages which will
remember about the user ?
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Client-Based
Server-Based
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Client-Based
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Client
side
View
state
Cookies
Query
strings
Hidden
fields

Server-Based
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Server
side
Application
state
Database
Session
state

Client Side state management
Query String
For understand it you must aware about Request and
Response object
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Response Object
You can use this class to inject text into the page, jump to
other page etc.
Write
Redirect
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Request Object
Provides access to the current page request, including the
request headers, cookies, query string, and so on.
IsSecureConnection
Checks to see whether you are communicating via an
HTTPS secure protocol or not.
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Request Object
Request.Browser.Browser
Request.QueryString()
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Query string
Information that is appended to the end of a page URL.
You can use a query string to submit data back to your
page or to another page through the URL.
Query strings provide a simple but limited way to maintain
state information.
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Query string
For example in first page you collect information about your client,
name and use this information in your second page.
Take 2 forms
Take 1 textbox and one button
Response.Redirect("Page2.aspx?Name=" & TextBox1.Text
Request.QueryString("Name")
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Query string
Response.redirect(“Formname?” &
qry);
Response.redirect(“Formname?name=”
& value);
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Query string
Advantages
No server resources are required
Widespread support Almost all browsers and client
devices support using query strings to pass values.
Simple implementation
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Query string
Disadvantages
Potential security risks
The information in the query string is directly visible to the
user via the browser's user interface.
Limited capacity Some browsers and client devices
impose a 2083-character limit on the length of URLs.
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More than one Query string
Using &
Dim str As String
str = "PageRequest.aspx?Name=" & TextBox1.Text & "&" &
"Lname=" & TextBox2.Text
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View State
View State is used to remember controls state when
page is posted back to server.
You can store page-specific information
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View State
The view state is implemented with a hidden form field
called _VIEWSTATE, which is automatically created in
every Web page.
When page is created on web sever this hidden control is
populate with state of the controls and when page is posted
back to server this information is retrieved and assigned to
controls.
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View State
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View State
Go View Source
Each control on a Web Forms page has a
ViewState property.
Take example of DropdownList
Set Property EnableViewState=True
Take also one button
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View State
<%@ Page Language="VB" EnableViewState="false"
AutoEventWireup="false" CodeFile="frmViewState.aspx.vb"
Inherits="frmViewState" %>
By default true.
So, even if it’s all the controls has set the
property Enableviewstate=True but they are not
working.
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View State
Take 2 Buttons and 1 TextBox
Take one variable before all the coding
Assign that variable in one button click and display in
the textbox
Click and 2nd button and write the same logic.
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View State
no = 5
ViewState("No") = no
TextBox1.Text = ViewState ("No")
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So,Moral of the story about ViewState
EnableViewState property for each control
EnableviewState attribute of the @Page (Page directive)
View source _ViewState
Store value using ViewState(Key)

View State
Advantages
View state does not require any custom programming to
use. It is on by default to maintain state data on controls.
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View State
Enhanced security features
The values in view state are hashed, compressed, and
encoded for Unicode implementations, which provides more
security than using hidden fields.
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View State
Disadvantages
Performance considerations
Storing large values can cause the page to slow down when
users display it and when they post it.
This is especially relevant for mobile devices, where
bandwidth is often a limitation.
32

View State
Device limitations
Mobile devices might not have the memory capacity to store
a large amount of view-state data.
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Hidden Fields
You can store page-specific information.
This control is not visible when the application is viewed in
the browser.
Storage area for page specific.
You must submit your pages to the server using the HTTP
POST method
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Hidden Fields
Does not render in a Web browser.
However, you can set the properties of the hidden field.
A hidden field stores a single variable in its value property
and must be explicitly added to the page.
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Hidden Fields
Advantages
Widespread support
Almost all browsers and client devices support forms with
hidden fields.
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Hidden Fields
Hidden fields are standard HTML controls that require no
complex programming logic.
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Hidden Fields
Disadvantages
The information in the hidden field can be seen if the page
output source is viewed directly, creating a potential
security issue.
Encrypt and decrypt the contents of a hidden field, but
doing so requires extra coding and overhead.
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Hidden Fields
Because hidden fields are stored in the page itself, storing
large values can cause the page to slow
Storage limitations
If the amount of data in a hidden field becomes very large,
some proxies and firewalls will prevent access to the page
that contains them.
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Cookies
A Cookie is a small text file that the browser creates and
stores on the hard drive of your machine.
Cookie is just one or more pieces of information stored as
text strings.
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Cookies
Cookies are useful for storing small amounts of frequently
changed information on the client.
The cookie contains information the Web application can
read whenever the user visits the site.
Cookies are associated with a Web site, not with a specific
page, so the browser and server will exchange cookie
information.
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Cookies
Good example
1. A site conducting a poll might use a cookie simply as a
Boolean value to indicate whether a user's browser has
already participated in voting so that the user cannot
vote twice.
2. Ebay assigns you an ID
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Cookies
Good example
1. A site conducting a poll might use a cookie simply as a
Boolean value to indicate whether a user's browser has
already participated in voting so that the user cannot
vote twice.
2. Ebay assigns you an ID
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Cookies
Cookies can either be temporary or persistent.
When creating a cookie, you specify a Name and Value.
Each cookie must have a unique name.
You can also set a cookie's date and time expiration.
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Cookies
If you do not set the cookie's expiration, the cookie is
created but it is not stored on the user's hard disk.
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Sets - Cookies
Dim aCookie As New HttpCookie("lastVisit")
aCookie.Values("Name") = txtName.Text
aCookie.Values("Dt") =
DateTime.Now.ToString
aCookie.Expires = DateTime.Now.AddDays(1)
Response.Cookies.Add(aCookie)
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Gets - Cookies
If Not Request.Cookies("lastVisit") Is Nothing Then
txtNameR.Text =
Request.Cookies("lastVisit").Values("Name").ToStri
ng
txtDateR.Text =
Request.Cookies("lastVisit").Values("Dt").ToString
End if
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Cookies
Advantages
Simplicity
The cookie is a lightweight, text-based structure.
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Cookies
Advantages
Data persistence
Although the durability of the cookie on a client computer is
subject to cookie expiration processes on the client and user
intervention, cookies are generally the most durable form of data
persistence on the client.
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Cookies
Disadvantages
Size limitations
Most browsers place a 4096-byte limit on the size of a cookie,
although support for 8192-byte
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Cookies
User-configured refusal
Some users disable their browser or client device's ability to
receive cookies, thereby limiting this functionality.
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Cookies
Users can manipulate cookies on their computer, which can
potentially cause a security risk or cause the application that is
dependent on the cookie to fail.
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What is State Management?
Server-Based
Application state
Session state
Database
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Application State
Storing application wide-specific information such as objects
and variables.
All information stored in the application state is shared
among all the pages of the Web application by using the
HttpApplicationState class.
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Application State
The ideal data to insert into application state variables is
data that is shared by multiple sessions and does not
change often.
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Application State
Goto Global.asax
Find Counter : Session_Start
Application(“Cnt”)= Application(“Cnt”)= +1
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Application State
Application("Message") = "Welcome to the LJ”
Application("Cnt") = 0
Sub Session_Start(ByVal sender As Object,
ByVal e As EventArgs)
Application("Cnt") = Application("Cnt") + 1
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Application State
Advantages
Application state is easy to use
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Application State
Application scope
Because application state is accessible to all pages in an
application, storing information in application state can
mean keeping only a single copy of the information
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Application State
Disadvantages
Limited durability of data
Because global data that is stored in application state is
volatile, it will be lost if the Web server process containing it
is destroyed, such as from a server crash, upgrade, or
shutdown.
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Application State
Resource requirements
Application state requires server memory, which can affect
the performance of the server as well as the scalability of
the application.
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Session State
Use when you are storing short-lived information that is
specific to an individual session and security is an issue.
Do not store large quantities of information in session state.
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Session State
Session("FirstName") = FirstNameTextBox.Text
Session("LastName") = LastNameTextBox.Text
Each active ASP.NET session is identified and tracked using
a 120-bit.$
SessionID values are generated using an algorithm
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Session State
The scope of session state is limited to the current browser
session.
If different users are accessing a Web application, each will
have a different session state.
Create Login Form
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Session State
The scope of session state is limited to the current browser
session.
If different users are accessing a Web application, each will
have a different session state.
Create Login Form
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Session State
Advantages
Data persistence
Data placed in session-state variables can be preserved
through Internet Information Services (IIS) restarts and
worker-process restarts without losing session data because
the data is stored in another process space.
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Session State
Cookieless support
Session state works with browsers that do not support HTTP
cookies, although session state is most commonly used with
cookies to provide user identification facilities to a Web
application.
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Session State
Cookieless support
Session state works with browsers that do not support HTTP
cookies, although session state is most commonly used with
cookies to provide user identification facilities to a Web
application.
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Session State
Disadvantage
Session-state variables stay in memory until they are either removed
or replaced.
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Database
Database enables you to store large amount of information
pertaining to state in your Web application.
Sometimes users continually query the database by using
the unique ID, you can save it in the database for use
across multiple request for the pages in your site.
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Database
Advantages
Security
Access to databases requires rigorous authentication and
authorization.
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Database
Storage capacity
You can store as much information as you like in a
database.
Data persistence
Database information can be stored as long as you like, and
it is not subject to the availability of the Web server.
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Database
Disadvantage
Complexity
Using a database to support state management requires
that the hardware and software configurations be more
complex.
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Thanks
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State Management in ASP.NET

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