What is session state in asp.net

A session is defined as the period of time that a unique user interacts with a Web application.
Session state is a collection of objects, tied to a session are stored on a server.
Session State information is available to all pages opened by a user during a single visit

ASP.NET allows you to save values using session state, a storage mechanism that is accessible from all pages requested by a single Web browser session. Therefore, you can use session state to store user-specific information. Session state is similar to application state, except that it is scoped to the current browser session. If different users are using your application, each user session has a different session state. In addition, if a user leaves your application and then returns later after the session timeout period, session state information is lost and a new session is created for the user. Session state is stored in the Session key/value dictionary.

You can use session state to accomplish the following tasks:
i.Uniquely identify browser or client-device requests and map them to individual session instances on the server. This allows you to track which pages a user saw on your site during a specific visit.

ii.Store session-specific data on the server for use across multiple browser or client-device requests during the same session. This is perfect for storing shopping cart information.

iii.Raise appropriate session management events. In addition, you can write application code leveraging these events.

ASP.NET session state supports several different storage options for session data:

a.InProc Stores session state in memory on the Web server. This is the default, and it offers much better performance than using the ASP.NET state service or storing state information in a database server. InProc is fine for simple applications, but robust applications that use multiple Web servers or must persist session data between application restarts should use State Server or SQLServer.

b.StateServer Stores session state in a service called the ASP.NET State Service. This ensures that session state is preserved if the Web application is restarted and also makes session state available to multiple Web servers in a Web farm. ASP.NET State Service is included with any computer set up to run ASP.NET Web applications; however, the service is set up to start manually by default. Therefore, when configuring the ASP.NET State Service, you must set the startup type to Automatic.

c.SQLServer Stores session state in a SQL Server database. This ensures that session state is preserved if the Web application is restarted and also makes session state available to multiple Web servers in a Web farm. On the same hardware, the ASP.NET State Service outperforms SQLServer. However, a SQL Server database offers more robust data integrity and reporting capabilities.

d.Custom Enables you to specify a custom storage provider. You also need to implement the custom storage provider.

e.Off Disables session state. You should disable session state if you are not using it to improve performance.

Example:Sessions are created as soon as the first response is being sent from the client to the server, and session ends when the user closes his browser window or some abnormal operation takes place. Here is how you can use session variables fortransferring values. Below you can see a Session is created for the user and "Name" is the key, also known as the Session key, which is assigned the TextBox value.

// Session Created



Session["Name"] = txtName.Text; 

Response.Redirect("WebForm5.aspx");



// The code below shows how to get the session value.



// This code must be placed in other page.



if(Session["Name"] != null) 

    Label3.Text = Session["Name"].ToString();