What is session? What are uses of session?

Q. What is session? What are uses of session?

A session is a way to store information (in variables) to be used across multiple pages. Unlike a cookie, the information is not stored on the users computer rather session is stored in server.

When you work with an application, you open it, do some changes, and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are or what you do, because the HTTP address doesn't maintain state.

Session variables solve this problem by storing user information to be used across multiple pages (e.g. username, favorite color, etc.). By default, session variables last until the user closes the browser. So; Session variables hold information about one single user, and are available to all pages in one application.

Fig : For every client session data is stored seperately

The following example shows how to create session variables in an ASP.NET page for the first and last name of a user, and set them to values retrieved from TextBox controls.

Session["FirstName"] = FirstNameTextBox.Text;

Session["LastName"] = LastNameTextBox.Text;

and to show this on page:

string username = Session["FirstName"] as string;

label1.Text = "Welcome" + Username;

A session ends if a user has not requested or refreshed a page in the application for a specified period. By default, this is 20 minutes. If you want to set a timeout interval that is shorter or longer than the default, use the Timeout property.

The example below sets a timeout interval of 5 minutes:

<%

Session.Timeout=5

%>

Uses of session

-          Carrying information as a client travels between pages.

-          One page data can be stored in session variable and that data can be accessed from other pages.

-          Session can help to uniquely identify each client from another

-          Session is mostly used in ecommerce sites where there is shopping cart system.

-          It helps maintain user state and data all over the application.

-          It is easy to implement and we can store any kind of object.

-          Stores client data separately.

-          Session is secure and transparent from the user.

Disadvantages of session:

-          Performance overhead in case of large volumes of data/user, because session data is stored in server memory.