Cookies

Unfortunately, HTTP is a "stateless" protocol. This means that each visit to a site (or even clicks within a site) is seen by the server as the first visit by the user. In essence, the server "forgets" everything after each request, unless it can somehow mark a visitor .Cookies can accomplish this.

Cookies are a very important method for maintaining state on the Web. "State" in this case refers to an application's ability to work interactively with a user, remembering all data since the application started, and differentiating between users and their individual data sets.

What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With ASP, you can both create and retrieve cookie values.

Why do sites use Cookies ?

There are many reasons a given site would wish to use cookies. These range from the ability to personalize information (like on My Yahoo or Excite), or to help with on-line sales/services (like on Amazon Books or eBay), or simply for the purposes of collecting demographic information (like DoubleClick). Cookies also provide programmers with a quick and convenient means of keeping site content fresh and relevant to the user's interests. The newest servers use cookies to help with back-end interaction as well, which can improve the utility of a site by being able to securely store any personal data that the user has shared with a site (to help with quick logins on your favorite sites, for example).

How to Create a Cookie?

The "Response.Cookies" command is used to create cookies.

Note: The Response.Cookies command must appear BEFORE the tag.

In the example below, we will create a cookie named "firstname" and assign the value "Alex" to it:

<% Response.Cookies("firstname")="Alex" %>

It is also possible to assign properties to a cookie, like setting a date when the cookie should expire:

<% Response.Cookies("firstname")="Alex" Response.Cookies("firstname").Expires=#May 10,2012# %>

How to Retrieve a Cookie Value?

The "Request.Cookies" command is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named "firstname" and display it on a page:

<% fname=Request.Cookies("firstname") 
response.write("Firstname=" fname) %>

Output: Firstname=Alex

A Cookie with Keys

If a cookie contains a collection of multiple values, we say that the cookie has Keys.

In the example below, we will create a cookie collection named "user". The "user" cookie has Keys that contains information about a user:

<% Response.Cookies("user")("firstname")="John"
Response.Cookies("user")("lastname")="Smith"
Response.Cookies("user")("country")="Norway"
Response.Cookies("user")("age")="25" %>

Read all Cookies

Look at the following code:

<% Response.Cookies("firstname")="Alex" 
Response.Cookies("user")("firstname")="John"
Response.Cookies("user")("lastname")="Smith"
Response.Cookies("user")("country")="Norway"
Response.Cookies("user")("age")="25" %>

Assume that your server has sent all the cookies above to a user.

Now we want to read all the cookies sent to a user. The example below shows how to do it (note that the code below checks if a cookie has Keys with the HasKeys property):

<% dim x,y
     for each x in Request.Cookies response.write("

     ")
if Request.Cookies(x).HasKeys then
for each y in Request.Cookies(x)
response.write(x & ":" & y & "=" & Request.Cookies(x)(y))
response.write("")
next
else
Response.Write(x & "=" &
Request.Cookies(x) & "
")
end if
response.write "

"

next

%>

Output:

firstname=Alex

user:firstname=John

user:lastname=Smith

user:country=Norway

user:age=25