P1247676908eviYL

1
State Management
2
Problems of HTML

• Stateless
• When the page is delivered, the connection
  stopped.
• State
• Provides the ability to associate variables
  (information) with a specific user or a specific
  transaction

3
Session

• A statement that adds or updates a session state
  item
• Session("EMail") sEmail
• A statement that retrieves the value of a session
  state item
• Dim sEmail As String Session("EMail").ToString
• A statement that removes an item from session
  state
• Session.Remove("EMail")

4
Cookies

• Cookie or magic cookie
• A small chunk of privileged or secret data
• In the Web context
• A small amount of data stored by a Web browser

5
Cookies

• Two ways to create a cookie
• cookie New HttpCookie(name)
• cookie New HttpCookie(name, value)
• Common properties of the HttpCookie class
• Expires
• Name

6
Create Cookies

• Code that creates a session cookie
• Dim NameCookie As New HttpCookie("UserName",
  sUserName)
• Syntax to create a new object in VB
• Dim objName As New className()
• Code that creates a persistent cookie
• Dim NameCookie As New HttpCookie("UserName")
• NameCookie.Value sUserName
• NameCookie.Expires Now().AddYears(1)

7
A Procedure to Create a Cookie

• Private Sub AddCookie()
• Dim NameCookie As New HttpCookie("UserName",
  _
• txtUserName.Text)
• NameCookie.Expires Now.AddYears(1)
• Response.Cookies.Add(NameCookie)
• End Sub

8
A Procedure to Retrieve the Value of a Cookie

• Protected Sub Page_Load(ByVal sender As Object, _
• ByVal e As System.EventArgs) Handles
  Me.Load
• If Not IsPostBack Then
• If Request.Cookies("UserName") IsNot
  Nothing Then
• lblUserName.Text "Welcome back " _
• Request.Cookies("UserName").Valu
  e _
• "."
• End If
• End If
• End Sub

9
What about Privacy?

• Cookie cannot be used as a virus, and it cannot
  access your hard drive
• Cookies are being used for tracking people's
  browsing habits, and that makes a lot of people
  really uncomfortable.