State Management 2

1
State Management 2

• In ASP. Net

2
View State

• View state uses a hidden field when the form is
  posted to store state on behalf of a client.
• Each time a page is posted to itself, the
  contents of the __VIEWSTATE field are sent as
  part of the post.
• The primary use of view state is for controls to
  retain their state across post-backs, but it can
  also be used as a mechanism for storing generic
  client-specific state between post-backs to the
  same page.
• You can safely access the ViewState in your Load
  event handler.

3
Application and Session Objects Reloaded.

• Application contains a collection of data that
  is available across the entire application during
  the life of the application.
• Session contains data that is available across
  all pages accessed by a single user during a
  single session.
• You can write code to respond to Application and
  Session events in the global.asax file.

4
Session State

• Session state is maintained on a per-client
  basis.
• When a client first accesses any page in an
  application, an ASP.NET generated session ID is
  created.
• Session state is used for things like
• Shopping carts, Viewing preferences, other
• Session state is the most flexible and, in
  general, the most efficient means of maintaining
  client-specific state.

5
Session Events
6
Using the Session Object

• Session state is maintained on behalf of each
  client within an ASP.NET application.
• When a new client begins to interact with the
  application, a new session ID (or session key) is
  generated
• The ID is associated with all subsequent requests
  from that same client.
• The state is retained in memory on the server in
  the default session state configuration.
• By default, the session key is retained on the
  client side in a cookie. (there is an alternative
  in cases where cookies do not work)

7
Application State

• Application state is where information that is
  global to the application may be stored.
• For efficiency, this state is typically stored
  once and then read from many times.
• Often used for application statistics variables
  or constant global data
• Number of users who have accessed site
• Counts of different types of browsers
• Can prefetch static data from a database or file
• Should be used with care

8
Application Events
9
Using the Application Object

• Application object is implicitly locked for you
  when data is read from or written to it.
• May make more sense to avoid using application
  object and use data cache if you are just storing
  global constants.
• Application object must be used if you are using
  shared, updatable data.