Slide 14.4: The Hashtable object

The Hashtable Object

The Hashtable object contains items in key/value pairs. The keys are used as indexes, and the values can be searched through their keys. Items are added to the Hashtable with the Add method. A Hashtable object may automatically generate the text and values to the following controls: RadioButtonList, CheckBoxList, DropDownList, and Listbox. To bind data to a RadioButtonList control, the example takes the following steps:

Create a RadioButtonList control (without any ListItem) in a page.
Add the script that builds the list.
Add a sub routine to be executed when the user clicks on an item in the RadioButtonList control.

demo_hashtable_radio1.aspx Web

01<%@ Page Language="VB" %>
02<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
03  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
04 
05<script language="VB" runat="server">
06 Sub Page_Load(s As Object, e As EventArgs) Handles Me.Load
07  If Not Page.IsPostBack Then
08   dim mycountries = New Hashtable
09   mycountries.Add( "N", "Norway" )
10   mycountries.Add( "S", "Sweden" )
11   mycountries.Add( "F", "France" )
12   mycountries.Add( "I", "Italy"  )
13   rb.DataSource = mycountries
14   rb.DataValueField = "Key"
15   rb.DataTextField  = "Value"
16   rb.DataBind( )
17  End If
18 End Sub
19 
20 Sub displayMessage( s as Object,e As EventArgs )
21  lbl1.text = "Your favorite country is: " & _
22    rb.SelectedItem.Text
23 End Sub
24</script>
25 
26<html xmlns="http://www.w3.org/1999/xhtml" > 
27 <body> 
28  <form runat="server">
29   <asp:RadioButtonList id="rb" runat="server"
30     AutoPostBack="True"
31     onSelectedIndexChanged="displayMessage" />
32   <asp:label id="lbl1" runat="server" />
33  </form>
34 </body>
35</html>