ASP.NET Web Forms - The Hashtable Object
The Hashtable object contains items in key/value pairs.
Examples
Create a Hashtable
The Hashtable object contains items in key/value pairs. The keys are used as indexes, and very quick searches can be made for values by searching through their keys.
Items are added to the Hashtable with the Add() method.
The following code creates a Hashtable named mycountries and four elements are added:
<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
dim mycountries=New Hashtable
mycountries.Add("N","Norway")
mycountries.Add("S","Sweden")
mycountries.Add("F","France")
mycountries.Add("I","Italy")
end if
end sub
</script>
Data Binding
A Hashtable object may automatically generate the text and values to the following controls:
- asp:RadioButtonList
- asp:CheckBoxList
- asp:DropDownList
- asp:Listbox
To bind data to a RadioButtonList control, first create a RadioButtonList control (without any asp:ListItem elements) in an .aspx page:
<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server"
AutoPostBack="True" />
</form>
</body>
</html>
Then add the script that builds the list:
<script runat="server">
sub Page_Load
if Not Page.IsPostBack then
dim mycountries=New Hashtable
mycountries.Add("N","Norway")
mycountries.Add("S","Sweden")
mycountries.Add("F","France")
mycountries.Add("I","Italy")
rb.DataSource=mycountries
rb.DataValueField="Key"
rb.DataTextField="Value"
rb.DataBind()
end if
end sub
</script>
<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server"
AutoPostBack="True" />
</form>
</body>
</html>
Then we add a sub routine to be executed when the user clicks on an item in the RadioButtonList control. When a radio button is clicked, a text will appear in a label:
Example
<script runat="server">
sub Page_Load
if Not Page.IsPostBack then
dim mycountries=New Hashtable
mycountries.Add("N","Norway")
mycountries.Add("S","Sweden")
mycountries.Add("F","France")
mycountries.Add("I","Italy")
rb.DataSource=mycountries
rb.DataValueField="Key"
rb.DataTextField="Value"
rb.DataBind()
end if
end sub
sub displayMessage(s as Object,e As EventArgs)
lbl1.text="Your favorite country is: " & rb.SelectedItem.Text
end sub
</script>
<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server"
AutoPostBack="True" onSelectedIndexChanged="displayMessage" />
<p><asp:label id="lbl1" runat="server" /></p>
</form>
</body>
</html>
Show example »
Note: You cannot choose the sort order of the items added to the Hashtable. To sort items alphabetically or numerically, use the SortedList object.
