ASP.NET Session state provides a place to store values that will persist across page requests.  Values stored in Session are stored on the server and will remain in memory until they are explicitly removed or until the Session expires.


C#

    Session["Name"] = "Hrishi"; // or Session.Add ("Name","Hrishi"); // retrievingstring

    Name = (string)Session["Name"];

By default the Session will be created within the same process that your web site runs in (InProc).  This is controlled by a setting in the web.config file:

    <sessionState mode="InProc" />

Although running the Session In Process is very convenient,  it does mean that all Session values will be lost whenever the application recycles (such as when deploying updates) .  There are alternate modes you can use that will allow the Session state to survive even when the application recycles.


    * Off - No session state will be stored
    * InProc - (The Default) Session state exists within the process the web is using
    * StateServer - Session data is sent to the configured stateserver service
    * SQLServer - Session data is store in the configured sql server database

Both the StateServer mode and the SQLServer mode allow Session state to survive an application recycle.  But, when storing reference type objects (such as class instances), they can only be stored to StateServer or SQLServer if they have been marked with the Serializable attribute.

An important consideration for using Session state is that the Session does expire.  By default, if a user does not access their Session data within 20 minutes (by default), the Session will expire and all items that had been stored in the Session will be discarded. Because of this, it is important to check the object that is returned from the Session to see if it exists or if it is null before you try to work with it. For example

object sessionObject = Session["someObject"];
if (sessionObject != null) {
 myLabel.Text = sessionObject.ToString();
}

The Session Timeout is adjustable through a web.config setting but increasing the timeout value can put memory pressure on your server that may be undesirable

     <sessionState timeout="number of minutes" />

Reference : MSDN

• The Custom module managed-code class. It is invoked during the Log request stage. 

ASP.NET offers a number of places to store state, both on the client and server. However, sometimes it's difficult to decide where you should put things and how to make that decision.

Application - Stored on the server and shared for all users. Does not expire.  Deprecated by Cache (below).

Cache - Stored on the server and shared for all users. Can expire.

Session - Stored on the server.  Unique for each user.  Can expire.

ViewState - Stored in a hidden page input (by default).  Does not expire.

Cookies - Stored at the client. Can expire.

QueryString - Passed in the URL.  Must be maintained with each request.

Context.Items - Only lasts for one request's lifetime.  More.

Profile - Stores the data in the database. Can be used to retain user data over multiple request and session.