StateManagement in ASP.Net.ppt

ASP.NET
State Management
Presented BY
A.M Rajole

Lecture Overview
 Client state management options
 Cookies
 Server state management options
 Application state
 Session state
 View state

Introduction to State
Management
 Remember that ASP.NET (and the Web) is
stateless
 The Web server does not keep track of past
client requests
 Different technologies handle the issue of
statement management differently
 ASP.NET is somewhat unique in this regard
 But PHP works similarly

Types of State Management
 ASP.NET offers two categories of state
management
 Pure client-side statement management
 Server-side state management
 We can use both concurrently

State Management (Issues)
 Client state management consumes
bandwidth and introduces security risks
because sensitive data is passed back and
forth with each page postback
 Preserving state on a server can overburden
servers
 We also must consider Web farms and Web
gardens

Web Farm
 A single ASP.NET application is hosted on
multiple web servers

Web Garden
 A single application pool contains multiple
worker processes run across multiple CPUs

Client State Management
(Introduction)
 View state
 Control state
 Hidden fields
 Cookies
 Query strings

State Management
(ViewState)
 ViewState works in a couple of different
ways
 It’s managed for you automatically via the
ASP.NET infrastructure
 Or you can take control yourself via the
ViewState object
 ViewState only provides state for a single
page
 It won’t work with cross page postbacks or
other page transfers

State Management
(ViewState) (auto)
 Just enable ViewState and the corresponding
control retains is value from one postback to the next
 This happens by default
 You can disable ViewState at the page level
 <%@ Page EnableViewState=”false” %>
 While simple, it does add overhead in terms of page
size
 MaxPageStateFieldLength controls the
maximum page size

State Management
(ViewState) (manual)
 ViewState can be set on the server up to
the Page_PreRenderComplete event
 You can save any serializable object to
ViewState
 The information is really just saved in hidden
fields
 See example ViewState.aspx

State Management
(ControlState)
 The ControlState property allows you to
persist information as serialized data
 It’s used with custom controls (UserControl)
 The wiring is not automatic
 You must program the persisted data each
round trip
 The ControlState data is stored in hidden
fields
 More later when (if) we create a user control

State Management
(Hidden Fields)
 Use the HiddenField control to store
persisted data
 The data is stored in the Value property
 It’s simple and requires almost no server
resources
 It’s available from the ToolBox and works
much like a text box control

State Management (Cookies)
 Use to store small amounts of frequently
changed data
 Data is stored on the client’s hard disk
 A cookie is associated with a particular URL
 All data is maintained as client cookies
 Most frequently, cookies store personalization
information

Cookie Limitations
 While simple, cookies have disadvantages
 A cookie can only be 4096 bytes in size
 Most browsers restrict the total number of
cookies per site
 Users can refuse to accept cookies so don’t
try to use them to store critical information

Cookies Members
 Use the Response.Cookies collection to
reference a cookie
 Value contains the cookie’s value
 Expires contains the cookie’s expiration date
 Cookies can also store multiple values using
subkeys
 Similar to a QueryString
 It’s possible to restrict cookie scope by setting
the Path property to a folder
 See example cookies.aspx

State Management
(Query Strings)
 As you know, query strings are just strings
appended to a URL
 All browsers support them and no server
resources are required

State Management
(Query Strings)
 HttpContext.Current.Request.RawURL
gets a URL posted to the server
 Or just use Request.QueryString
 HttpUtility.ParseQueryString breaks
a query string into key / value pairs
 It returns a NameValueCollection
 We will see how to do this later when we
work more with query strings an URLs

Server State Management
Options
 Application state
 Session state
 Profile properties
 Database support

Server State Management
 HttpApplicationState applies to your
entire application
 Application object
 HttpSessionState applies to the
interaction between a user’s browser session
and your application
 Session object
 Page caching also relates to state
management

The Application’s State
(Introduction)
 An instance of the HttpApplicationState
object is created the first time a client
requests a page from a virtual directory
 Application state does not work in a Web farm
or Web garden scenario
 Unless we push data to a database
 It’s volatile – If the server crashes, the data is
gone
 Unless we persist out of process
 It’s really just a collection of key/value pairs

The HttpApplicationState
Class (Members 1)
 The AllKeys property returns an array of
strings containing all of the keys
 Count gets the number of objects in the
collection
 Item provides read/write access to the
collection

Class (Members 2)
 StaticObjects returns a reference to
objects declared in the global.asax file
 <object> tags with the scope set to
Application
 The Add method adds a new value to the
collection
 The Remove method removes the value
associated with a key

Class (Members 3)
 Lock and Unlock lock the collection,
respectively
 Not an ASP topic but a thread synchronization
topic
 Get returns the value of a collection item
 The item can be referenced by string key or
ordinal index
 Set store a value corresponding to the
specified key
 The method is thread safe

Application State
(Best Practices)
 Memory to store application state information
is permanently allocated
 You must write explicit code to release that
memory
 So don’t try to persist too much application state
information
 The Cache object, discussed later, provides
alternatives to storing application state
information

Profile Properties
 It’s a way to permanently store user-specific
data
 Data is saved to a programmer-defined data
store
 It takes quite a bit of programming
 The whole thing is unique to windows
 We will not use profiles in this course

Profiles (Enabling)
 Web.config must be modified to enable
profiles
 You can then reference with code as follows

Session State (Introduction)
 It is used to preserve state for a user’s
‘session’
 Session state works in Web farm or Web
garden scenarios
 Since the data is persisted in the page
 Session data can be stored in databases such
as SQL Server or Oracle making it persistent
 It’s very powerful and the features have been
significantly enhanced in ASP 2.0

Session State (Configuration)
 The <web.config> file contains a
<sessionState> section
 The entries in this section configure the state
client manager

Web.Config
<sessionState>
<sessionState mode="[Off|InProc|StateServer|SQLServer|Custom]"
timeout="number of minutes" cookieName="session identifier
cookie name" cookieless=
"[true|false|AutoDetect|UseCookies|UseUri|UseDeviceProfile]
" regenerateExpiredSessionId="[True|False]"
sqlConnectionString="sql connection string"
sqlCommandTimeout="number of seconds"
allowCustomSqlDatabase="[True|False]"
useHostingIdentity="[True|False]"
stateConnectionString="tcpip=server:port"
stateNetworkTimeout="number of seconds"
customProvider="custom provider name">
<providers>...</providers> </sessionState>

Session State Providers (1)
 Custom – State information is saved in a
custom data store
 InProc – State information is preserved in
the ASP.NET worker process named
(aspnet_wp.exe or w3wp.exe)
 This is the default option
 Off – Session state is disabled

Session State Providers (2)
 SQLServer – State data is serialized and
stored in an SQL server instance
 This might be a local or remote SQL Server
instance
 StateServer – State information is stored
in a separate state server process
(aspnet_state.exe)
 This process can be run locally or on another
machine

Session State Providers
(Best Practices)
 Use an SQL server provider to ensure that
session state is preserved
 Note that there is a performance hit here
because the session information is not stored in
the page
 The InProc provider is not perfect
 The ASP worker process might restart thereby
affecting session state

Session State Identifiers
 Browser sessions are identified with a unique
identifier stored in the SessionID property
 The SessionID is transmitted between the
browser and server via
 A cookie if cookies are enabled
 The URL if cookies are disabled
 Set the cookieless attribute to true in the
sessionState section of the Web.config file

HttpSessionState
(Members 1)
 CookieMode describes the application’s
configuration for cookieless sessions
 IsCookieless is used to depict whether
cookies are used to persist state
 IsNewSession denotes whether the session
was created with this request
 SessionID gets the unique ID associated
with this session
 Mode denotes the state client manager being
used

HttpSessionState
(Members 2)
 Timeout contains the number of minutes to
preserve state between requests
 Abandon sets an internal flag to cancel the
current session
 Add and Remove add or remove an item to
the session state
 Item reads/writes a session state value
 You can use a string key or ordinal index value

StateManagement in ASP.Net.ppt

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