Session State Modes in ASP.NET

ASP.NET session state supports several different storage options for session data. Each option is identified by value in the SessionStateMode enum. ASP.NET Session has the type HttpSessionStateBase type. Session has 2 methods, Session.Clear() and Session.Abandon(). See the difference.

InProc (default)

Store session state in web server memory.

StateServer 

• Store session state in a separate process called ASP.NET state service. 
• This ensures session state is preserved if the web app is restarted. 
• Makes session state available to multiple web servers in a server farm. 
• If using stateServer the objects stored in the session should be serializable. 
• If using in a server farm you must have same machine key in all machines. 

SQL Server

• Store in SQL Server DB. Same as state server, ensures preservation of data when web app restarted and on web farms. 
• Objects should be serializable
• You must first install ASP.NET session state database in SQL Server
• You can use fail over cluster 

Custom

Enables you to specify custom storage provider. See how to implement session state store provider. There's one for Redis.

Off

Disable session state
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HttpSessionState 

• Provides access to session-state values as well as session-level settings and lifetime management methods.
• Enables you to store information associated with a unique browser session across multiple requests
• Can access these through Session property of the current HttpContext, or Session property of the Page
• Session data is associated with a specific browser using a unique identifier. By default, this identifier is stored in non-expiring cookie in the browser.
• You can also use Timeout property set a timeout
• When a new session begins session Start event is raised
• When session times out, the Abandon method is called.
• When ASP.NET application shut down the session End event is raised. (The End event is raised only when the session state mode is set to InProc)
• Session state does not persist across application boundaries
• Session values are stored in the memory of the web server.

Session object in ASP.NET

http://stackoverflow.com/questions/2874078/asp-net-session-sessionid-changes-between-requests
http://stackoverflow.com/questions/tagged/sessionid
http://stackoverflow.com/questions/940742/difference-between-session-and-httpcontext-current-session

In ASP.NET For session state management we have,

• View State
• Control state
• Hidden fields
• Cookies
• Query Strings

ASP.NET MVC doesn't have view state or postbacks.

Changing ASP.NET_SessionId cookie name
http://stackoverflow.com/q/1017144/340046

Resources
Session-State Modes - MSDN
http://blogs.msdn.com/b/kenkilty/archive/2014/07/03/asp-net-session-state-using-sql-sever-in-memory.aspx