HttpSessionState.Timeout Property
Gets and sets the amount of time, in minutes, allowed between requests before the session-state provider terminates the session.
Namespace: System.Web.SessionState
Assembly: System.Web (in System.Web.dll)
The Timeout property can be set in the Web.config file for an application using the timeout attribute of the sessionState configuration element, or you can set the Timeout property value directly using application code.
The Timeout property cannot be set to a value greater than 525,600 minutes (1 year). The default value is 20 minutes.
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.