HttpSessionState

HttpSessionState is a server-side storage mechanism used by ASP.NET applications to preserve user-specific data across multiple HTTP requests within the same session. It provides a per-user, per-session key-value store that developers can use to keep information such as authentication status, user preferences, or intermediate form data while a user navigates through pages.

A session is identified by a session ID, typically stored in a cookie, and is created automatically when a request accesses the Session object. The session remains active until it times out, the user’s session is abandoned, or the application explicitly calls Abandon. The Timeout property configures how many minutes of inactivity are allowed before the session expires, with a default value commonly set in the application configuration.

Data in HttpSessionState is accessed via an indexer, such as Session["Key"] to get or set values. The API also exposes methods such as Add, Remove, Clear, and Abandon, and a collection of Keys to enumerate stored values. This class is usable with code-based access patterns or simple declarative session usage in the page or controller logic.

HttpSessionState supports several storage modes, controlled by the SessionStateModule configuration: InProc (stored in the worker process memory), StateServer (out-of-process), SQLServer (persisted in a SQL Server database), and a custom provider. When using out-of-process modes, objects stored in session must be serializable to be transferred across process boundaries.

Security considerations include protecting the session identifier (use HTTPS to prevent interception), minimizing the amount of sensitive data stored in the session, and configuring appropriate timeout values to reduce exposure risk.

See also: HttpSessionStateBase, SessionStateModule, and ASP.NET session configuration.