Lesson_12 Cookies

8/7/2019 Lesson_12 Cookies

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WebEngineeringII UsingASP.net

By

Adnan AminLec turer / Softw are p rog rammer

Information and Comm unica tion Tec hnology (ICT-Dep t)

www.geoamins.com


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Why cookies. Cookies seem to solve the prob lem of moving data

from page to page.

Cookies can be stored so that it remains there after

the user leaves your site and will still be ava ilablewhen the user entered your web site a hour, day, or

month later.

Cookies were originally designed for storing smallamounts of information for short periods of time.

By: Adna n Am in(Lecturer/Programmer)

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Introduction

to

cookies

The place (file) which can store small amounts ofinformation that containing variable=value pairs. The users browser stores cookies on the userscomputer. The stored data can use again and again until thecookies is available on the users computer. Cookies should be used only to store non-sensitive

information, or information that can be retrieved froman authoritative sourc e. Cookies shouldnt be trusted.


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Limitationsof

cookies

Cookies are not under your control. They are under the userscontrol.

The user can at any time delete the c ookie.

Users can set their browsers to refuse to allow any cookies.

Many users do refuse cookies or routinely delete them.

Many users are not comfortable with the idea of a strangerstoring things on their computers.

Cookie size is limited to 4096 bytes. It is not much, so cookies

are used to store small amounts of da ta, often just user id.

Also, number of cookies is limited to 20 per website. If youmake new c ookie when you already have 20 cookies, browserwill delete oldest one


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Remember

When you store information in cookies,remember that its quite different from

storing data in the Session object:


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ToseewhereIE7&8storesitsCookiesinWindowsVista/7:

OpenExplorer>Organize>FolderOptions>Views>Check Donotshowhiddenfilesandfolders andUncheck HideprotectedOSfiles >Apply>OK.

NowyouwillbeabletoseethetworeallocationsofVistasCookiesfolders.

C:\Users\username\AppData\Roaming\Microsoft\Windows\Cookies


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CookiesTerminologies

READING COOKIES

Read cookies using Request.Cookiescollectiono Request is ac tua lly an HTTPRequest objec t

o Each objec t is a HTTPCookiesCollec tion consisting ofHTTPCookie objec ts.

WRITING COOKIES Response is ac tua lly an HTTPResponse objec t.


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Createaninstanceofacookiethen

addittothecollection.

Dim cookie As HttpCookie = New HttpCookie("myCookie")

cookie.Value = Me.TextBox1.Text

cookie.Exp ires = DateTime.Now.AddDays(1)

Response.Cookies.Add(cookie)


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Createdirectlycookieforthesameuser.

Response.Cookies("UserID").Va lue = TextBox1.Text

Response.Cookies("UserID").Expires =DateTime.Now.AddDays(1)


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Createaninstanceofacookie,

thenaddtwosubkeys,andaddittothecollection.

Dim c ookie1 As HttpCookie = NewHttpCookie("UserData")

cookie1.Values("LastVisit") =DateTime.Now.ToString()

cookie1.Values("UserID") = TextBox1.Text

cookie1.Exp ires = DateTime.Now.AddDays(1) Response.Cookies.Add(cookie1)


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Readacookiebycreating

aninstanceofthecookie.

If Not Request.Cookies("myCookie") Is Nothing Then Dim cookie As HttpCookie =

Request.Cookies("myCookie")

Label2.Text = cookie.Value

Else

Label2.Text = "the c ookie is not found"

End If


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Reada

cookie

value

directly,

encodingitforsafety.

If Not Request.Cookies("UserID") Is Nothing Then

Label3.Text = Request.Cookies("UserID").Value

End If


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Readasubkey valueinacookiedirectly.

If Not Request.Cookies("UserData") Is Nothing Then Label4.Text = Request.Cookies("UserData")("UserID")

Label5.Text = Request.Cookies("UserData")("LastVisit")

End If


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Delete

a

cookie

by

setting

theexpirationtoa

previousdate/time.

Response.Cookies( myCookie").Exp ires =DateTime.Now.AddDays(-1)


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Howtocheckdoesvisitors

webbrowsersupportscookies If Request.Browser.Cookies Then

' Cookies supportedElse' Web browser not supports c ookies

End If


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DeleteaSubkey

value

by

removingit.

Response.Cookies("UserData").Values.Remove("LastVisit")


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ThankYou!


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Lesson_12 Cookies

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Transcript of Lesson_12 Cookies