Page and Application Context in ASP.NET Web Applications

When a Web application runs, ASP.NET maintains information about the current application, each user session, the current HTTP request, the requested page, and so on. ASP.NET contains a series of classes to encapsulate this context information.

ASP.NET makes instances of these classes available as intrinsic objects that you can access from your code. The following table lists these intrinsic objects and the classes they are instances of.

Object Name	Description	ASP.NET Class
Response	Provides access to the output stream for the current page. You can use this class to inject text into the page, to write cookies, and more. For details, see System.Web.UI.Page.Response property.	HttpResponse
Request	Provides access to the current page request, including the request headers, cookies, client certificate, query string, and so on. You can use this class to read what the browser has sent. For details, see System.Web.UI.Page.Request property.	HttpRequest
Context	Provides access to the entire current context (including the request object). You can use this class to share information between pages. For details, see System.Web.UI.Page.Context property.	HttpContext
Server	Exposes utility methods that you can use to transfer control between pages, get information about the most recent error, encode and decode HTML text, and more. For details, see System.Web.UI.Page.Server property.	HttpServerUtility
Application	Provides access to application-wide methods and events for all sessions. Also provides access to an application-wide cache you can use to store information. For details, see ASP.NET Application State.	HttpApplicationState
Session	Provides information to the current user session. Also provides access to a session-wide cache you can use to store information, along with the means to control how the session is managed. For details, see ASP.NET Session State.	HttpSessionState
Trace	Provides a way to display both system and custom trace diagnostic messages in the HTTP page output. For details, see ASP.NET Tracing.	TraceContext

The following topics show examples of how the intrinsic objects can be used.

Object	Example topics
Application	How to: Read Values from Application State How to: Save Values in Application State
Request	How to: Read a Cookie How to: Write a Cookie
Server	How to: Handle Application-Level Errors How to: Handle Page-Level Errors
Session	How to: Save Values in Session State How to: Read Values from Session State

See Also

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