CIS 451: ASP Sessions and Applications

Dr. Ralph D. WestfallJanuary, 2009

State Handling http server only processes

requests for web pages, images, etc.

this is a "stateless" connection server sends page, etc. and writes

some tracking data to a log file but does NOT store any information in

its memory about the request

State Handling - 2 ASP.NET can store some information

in memory in relation to web site visitors, which can be used to: make frequently used/updated

information available to several/all pages in site

store information about a page so it will be available when page is loaded again

pass information between pages

Definitions Application: group of web pages

working together for a common purpose often in same directory or its

subdirectories Session: a client accessing an

application Cookie: data stored by the

application on a client's computer

Session State session starts when a user accesses a

page ends after a time period, or when closed

by ASP code data can be stored in "session variables"

stored in Session Contents collection available until session ends, then lost user's browser must accept cookies

without cookies, can't use session variables

Accessing Contents Collection session contents "indexed" by "keys" writing to Session contents:

Session("intCount") = intCount

reading from Session contents: intNumber = Session("intCount")

variable name before = does NOT have to match names of keys when reading or writing using same names can help in

maintenance

Session Object Properties SessionID: unique identifier for session Timeout : when session ends if no

activity (default often is 20 minutes) Session.Timeout = 30 'ends 30 minutes

international settings (currency) CodePage (sets character alphabet) LCID (locale ID values set time zone and

other location information, but only if installed on server)

Session Object Methods Abandon: ends session before it

times out Session.Abandon() removing Session contents data

Session.Clear()

Problem with Session Variables user's browser must accept cookies

without cookies, can't use session variables

alternative: userID and password requires customer to establish an account data stored in database on server requires writing extra HTML code into

each page (hidden form fields) to identify the user who is requesting another page

Application State includes variables that can be available

to all pages in the "application" variables can be set/changed from a web

page via authorized inputs can also be stored in a Global.asax file

value loads into memory every time server is turned on (but changing a value(s) in memory does NOT update this file)

An Application includes all files in a virtual directory

("root"), and in its subdirectories starts when first client opens any of files can have many sessions (users)

accessing it at the same time (simultaneously) number of sessions limited only by

available memory of server

An Application - 2 continues until server shuts down

usually means something went wrong also ends when application is

"unloaded" from server can use Microsoft Management

Console to unload

Application State Items are stored data useable in all sessions stored in Application Contents

collection "initialized" in Global.asax file (can view in

Visual Studio) in application's root directory

Sub Application_Start(ByVal sender _ As Object, ByVal e As EventArgs)

Application("dblPrice1") = 1.50 Application("dblPrice2") = 2.75 End Sub

Accessing Application State Items reading is like reading Session variables dblPrice(1)= Application("dblPrice1") writing requires "concurrency control" Application.Lock() Application("hits") += 1 Application.Unlock()

lock so other users can't access until done writing overrides values in Global.asax file

does NOT change contents of Global.asax

Global.asax and Web.config Global.asax: settings that won't change use Web.config file for anything that

could change instead of Global.asax can store objects as well as variables e.g.,

connection string if either file has a lot of items, check

code to avoid duplications in other files