CIS 451: ASP Sessions and Applications Dr. Ralph D. Westfall January, 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)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 connection string if either file has a lot of items, check code to avoid duplications in other files