ASP.NET State Management

ASP.NET State Management
ASP.NET includes a variety of options for state management. It features the same Session and Application
state collections as traditional ASP (with a few enhancements) and an entirely new view state
model. ASP.NET even includes a caching system that allows you to retain information without sacrificing
server scalability. Each state management choice has a different lifetime, scope, performance
overhead, and level of support.
下表是Collection-based state.

	View State	Custom Cookies	Session State	Application State	Caching
Allowed Data Types	All serializable .NET data types.	String data.	All serializable .net date types Nonserializable types are supported if you are using the default in-process state service	All .NET data types	All .NET data types
Storage Location	A hidden field in the current web page.	The client’s computer (in memory or a small text file, depending on its lifetime settings).	Server memory	Server memory	Server memory
Lifetime	Retained permanently for postbacks to a single page	Set by the programmer. It can be used in multiple pages and can persist between visits.	Times out after a predefined period(usually 20 minutes)	The lifetime of the application	Depends on the expiration policy you set but may possibly be released early if server memory becomes scarce.
Scope	Limited to the current Page	The whole asp.net application	The whole ASP.NET application	The whole ASP.NET application .Unlike most other types of the methods .application data is global to all users	The same as application state
Security	By default it’s insecure, although you can use Page directives to enforce encryption and hashing.	Insecure and can be modified by the user	Secure.because the data is never transmitted to the client.However, subject to session hijacking if you don not use SSL	Very secure.because the data is never transmitted to the client.	Very secure.because the data is never transmitted to the client.
Performance Implications	Storing a large amount of information will slow transmission but will not affect server performance	None,because the amount f the data is trivial.	Storing a large amount of information can slow down the server severely. Especially if  there are a large number of user will have a separate copy of sessiondata.	Storing a large amount of information can slow down the server severely. Because this data will never time out and be removed	Storing a large amount of information may force out other , more useful cached information. However ,ASP.NET has the ability to remove items early to ensure optimum performance.
Typical Use	Page-specific settings	Personalication preferences for website	Store items in a shopping basket.	Storing any types of global data	Storing data retrieved from a databse

 

	Profiles	Query String
Allowed Data Types	All serializable .NET data types Nonserializable types are supported if you create a custom profile.	A limited amount of string data.
Storage Location	A back-end database.	The browser’s URL string.
Lifetime	Permanent.	Lost when the user  enters a new URL or closes the browser. However, can be stored in a bookmark.
Scope	The whole ASP.NET application.	Limited to the target page
Security	Fairly secure, because although stored in a database that could be compromised.	Clearly visible and easy for the user to modify.
Performance Implications	Large amounts of data can be stored easily, but there may be a nontrivial overhead in retrieving and writing the data for each request.	None, because the amount of data is trivial.
Typical Use	Store customer account information.	Sending a product ID from a catalog page to a details page.