Understanding Session

A session is defined as a period of time that is shared between the web application and the user. Each user that is using the web application has their own session. Items/Objects can be placed into the Session which would only define these object for that user. Session contains key variables which help to identify the related values. This can be thought of as a hash table. Each user would represent a different key node in the hash identifying unique values. The Session variables will be clear by the application which can clear it, as well as through the timeout property in the web config file.

A practical example would be a web application where a user logs into. Each user that logs into your system will have a unique session. We can hold additional data into the session which can be used as the user browses your site. We can hold the first name, last name, and other data simply by adding it to the session:

Session[“FirstName”] = “User First Name”;
Session[“LastName”] = “User Last Name”;

We can clear the session variable by doing the following:

Session[“FirstName”] = null;

We can clear all Session variables by dong the following:

Session.Abandon();

A Session variable should be used with respect to the individual user. It stores the information on the server side and should not be taken advantage of. The difference between the cache and session is that the cache is available to be accessed from the global/application level where one reference to memory is updated. Each request will use the same cache for different users. Session variables will use different session variables for each different user. Usually a large amount of data can be stored on the session, however web sites that have a large amount of traffic usually would not use this method, as it would put a severe load on the server memory.