Sessions - How To Pass Information Between Web Pages

[Frinavale]

One of the most fundamental topics in web design is understanding how to pass information collected on one web page to another web page. There are many different ways you could do this: Cookies, Database... However, I'm going to cover how to use Sessions.

Sessions are used to store information in order to use it during later page requests or in other web pages in a web application. By default Cookies are used to identify which session belongs to which browser. There is an option that you can set in your web.config file to use Cookieless Sessions; however you should keep in mind that for most web applications the Session ID should be kept private and when using Cookieless Sessions the Session ID is displayed in the query string.

In .NET there are three session states: InProc, StateServer, and SQLServer.
By default web applications are set up to use InProc.


Where are Sessions stored?
InProc
The session is kept as live objects on web server (aspnet_wp.exe) . It is stored in memory and is the fastest out of the three options; however, you should keep in mind that the more data you store in session, the more memory on the web server is consumed. This could affect the performance of your applications running on the web server. Also keep in mind that you cannot use InProc sessions in a web garden for many reasons I'm not going to get into.

StateServer
The session is serialized and stored in memory in a separate process (aspnet_state.e xe). State Server can run on another machine, whereas InProc is specific to the machine the website is running on. You should keep in mind that the cost of serialization/deserialization of the session can affect performance if you're storing lots of objects.

SQLServer
The session is serialized and stored in a table in an SQL server. It requires you have a database available and you should think about how you are going to secure the connection to the database. This is the slowest of the three options but is required in order to store persistent data.

How do I use Sessions in my web application

It's really quite simple.
In the following example I use VB.NET to store the text value (userName) of a text box in session during a button click:

 Private Sub btn_button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn_button1.Click
   Session("userName") = txt_userName.Text
End Sub
 

In the following example I use VB.NET to display the text value (userName) stored session. This can be used on another web page within the web application:

 Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
     Dim userName as String = Session("userName")
     lbl_welcome.Text= "Welcome to working with Sessions " + userName + "!"
End Sub
 

[Frinavale]

i am aware of 1st 4 types u explaied including viewstate. but i have 1 doubt.
hiddenfield n hiddenframe r wh exactly , r they related to viewstate or something different, can u explain hiddenfield n hiddenframe more

ViewState is used to remember the state of your ASP.NET controls.
Hidden Fields are html that hold temporary information for the page...it remembers information but not necessarily about an ASP.NET Control.

Hidden fields can be used to pass information between JavaScript and your .NET code. Eg. your JavaScript function does something and then stores the result into a hidden field, this filed can then be accessed by the server side code to do further calculations.

-Frinny

[Ewan]

Hi Frinavale, thanks for this info.
i had a doubt, i have i multiple users who would be accessing different records at the same time.
and if im using Session to pass the values as required, could this result in a slow performance for my web app. also is there any way to remove a session after the value is passed..
would this affect another user if his command(button click) tries to create the session again with the same name?

[Frinavale]

If you have several users then you, and you are storing a lot of information in session, then you run the risk of using a lot of memory resources on the server computer. If you use more memory than is allocated to your website, then the web application process will be recycled.

I'm not sure about the effects of speed performance Session will have on your application; however, it is much faster than accessing a database every request. (Likewise storing things in ASP.NET's Cache is even faster).

Do some tests to determine what is best for your solution.


-Frinny

[Akbar Abro]

Thanks u sir i have don it.... love this forum