Cookies: - Cookies are little pieces of information
that a server stores on a browser. They are of two types
- Temporary
cookie
- Persistent
cookie
Temporary cookie: - They are also known as session
cookies. These are volatile in nature. When the browser is shutdown they are
erased.
Persistent cookie:- These may be called as permanent
cookies. These are especially saved in files. It may remain for a month or
year.
Properties of cookies
Some properties of cookie
Name: - represent the name of cookie.
Name value: - represent a collection of key values of cookie
Domain: - represent the domain associated with a specific
cookie.
Path: - the path associated with a cookie.
Expires: - expired time of cookie.
Hashkey: - identifies whether the cookie is a cookie dictionary.
Secure: - specifies whether the cookie is to be sent in an
encrypted connection or not.
Working with cookies
Cookies are send back and forth between a browser and
server. The server creates a cookie by using the set cookie header. Subsequent
request from the browser is send to the server in cookie header. Suppose the
server create a cookie
Set cookie: username=rajkumar; path=1;domain=abc.com;
expires=Friday, 19th august 20116:30:00GMT
The server creates the cookie named as username containing
the user information. Path identifies any requested page to the website, domain
identifies the specific website abc.com, expired identifies that this cookie
would be expired on the specific data mentioned.
After the server creates the cookie the response is send to
the server from the browser for each subsequent request to the webpage. The
reader sends in the format cookie: username=raj+kumar
The server is using set cookie reader. The browser is using
reader.
Creation and reading session cookies
The session cookies can be created by using the response
object and can be read by using the request object. The cookies properties of
the response and request objects contains instances of Httpcookies collection
class. Each cookie is created by using Httpcookie class.
For creating cookies
Dim cookies1 As New HttpCookie(“raj”, “kumar”)
Response.Cookies.Add(cookies1)
For reading cookies
Response.Write(request.cookies(cookies1).value)
Program
Partial Class
_Default
Inherits System.Web.UI.Page
Protected Sub Button1_Click(ByVal
sender As Object,
ByVal e As
System.EventArgs) Handles Button1.Click
'For creating cookies
Dim cookies1 As New
HttpCookie(TextBox1.Text, TextBox2.Text)
Response.Cookies.Add(cookies1)
clear()
End Sub
Protected Sub Button2_Click(ByVal
sender As Object,
ByVal e As
System.EventArgs) Handles Button2.Click
'For reading cookies
Dim s As String
For Each s In Request.Cookies
Label1.Text += "<li>"
& s
Next
End Sub
Sub clear()
TextBox1.Text = ""
TextBox2.Text = ""
End Sub
End
Class
Persistence cookies
It is saved in a config file.it has a specific expiration
date. It is especially used to store information about userid, name of authenticated
user.
For creating persistence cookie
Dim pcookie1 as New HttpCookie(“user name”.”ravi kumar”)
Response.Cookies.Add(pcookie1)
pcookie1.expires= #19/06/2011#
For reading persistent cookie
Response.Write(Request.cookies(“user name”).Value)
Limitation of cookies: -
1.A cookie can store maximum of 4kb of data.
2.A cookie can contain only string values. It can contain
objects like dataset object.
3.A cookie is browser dependent.
4.Persistent cookie may be deleted before expiration date by
browser.