a System.Web.SessionState.HttpSessionState
This property provides information about the current request's session. A Session object is maintained for each user that requests a page or document from an ASP.NET application. Variables stored in the Session object are not discarded when the user moves from page to page in the application; instead, these variables persist as long as the user is accessing pages in your application. For more information about session state, see ASP.NET Session State Overview.