what is diff. b/w app state & session state

浏览数：30 / 时间：2015年06月11日

　　Application state is a data repository available to all classes in an ASP.NET application. Application state is stored in memory on the server and is faster than storing and retrieving information in a database. Unlike session state, which is specific to a single user session, application state applies to all users and sessions. Therefore, application state is a useful place to store small amounts of often-used data that does not change from one user to another.

　　ASP.NET session state enables you to store and retrieve values for a user as the user navigates ASP.NET pages in a Web application. HTTP is a stateless protocol. This means that a Web server treats each HTTP request for a page as an independent request. The server retains no knowledge of variable values that were used during previous requests. ASP.NET session state identifies requests from the same browser during a limited time window as a session, and provides a way to persist variable values for the duration of that session.By default, ASP.NET session state is enabled for all ASP.NET applications.

Alternatives to session state include the following:

Application state, which stores variables that can be accessed by all users of an ASP.NET application.
Profile properties, which persists user values in a data store without expiring them.
ASP.NET caching, which stores values in memory that is available to all ASP.NET applications.
View state, which persists values in a page.
Cookies.
The query string and fields on an HTML form that are available from an HTTP request.