Visual Basic.NET How to Program (PDF)

Chapter 20 ASP .NET, Web Forms and Web Controls 991
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Fig. 20.29 Options supplied on an ASPX page (part 3 of 3).
Every Web Form includes an HttpSessionState object, which is accessible
through property Session of class Page. Throughout this section, we use property Session
to manipulate our page’s HttpSessionState object. When the Web page is
requested, an HttpSessionState object is created and assigned to the Page’s Session
property. As a result, we often refer to property Session as the Session object.
When the user presses Submit, submitButton_Click is invoked in the code-behind
file (Fig. 20.30). Method submitButton_Click responds by adding a key-value pair
to our Session object, specifying the language chosen and the ISBN number for a book
on that language. These key-value pairs are often referred to as session items. Next, a postback
occurs. Each time the user clicks Submit, submitButton_Click adds a new session
item to the HttpSessionState object. Because much of this example is identical
to the last example, we concentrate on the new features.
1 ' Fig. 20.30: OptionsPge2.aspx.vb
2 ' A listing of programming languages,
3 ' cookie is created based on choice made.
4
5 Imports System.Web.UI.WebControls
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7 Public Class Options2
8 Inherits System.Web.UI.Page
9 Protected WithEvents languageLink As HyperLink
10 Protected WithEvents recommendationsLink As HyperLink
11 Protected WithEvents LanguageList As RadioButtonList
12 Protected WithEvents idLabel As Label
13 Protected WithEvents timeOutLabel As Label
14 Protected WithEvents promptLabel As Label
15 Protected WithEvents welcomeLabel As Label
16 Protected WithEvents submitButton As Button
17 Private books = New Hashtable()
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19 ' Visual Studio .NET generated code
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21 Private Sub Page_Init(ByVal sender As System.Object, _
22 ByVal e As System.EventArgs) Handles MyBase.Init
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24 InitializeComponent()
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Fig. 20.30 Sessions are created for each user in an ASP .NET Web application (part 1
of 4).