ASP.NET - Hashtable Object

The Hashtable object contains items represented by key/value pairs.

Instance

Hashtable RadiobuttonList 1
Hashtable RadiobuttonList 2
Hashtable DropDownList

Create Hashtable

The Hashtable object contains items represented by key/value pairs. The key is used as an index, and by searching its key, a quick search of the value can be achieved.

Items are added to the Hashtable using the Add() method.

The following code creates a Hashtable named mycountries and adds four elements to it:

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim mycountries=New Hashtable
  mycountries.Add("C","China")
  mycountries.Add("S","Sweden")
  mycountries.Add("F","France")
  mycountries.Add("I","Italy")
end if
end sub
</script>

Data Binding

The Hashtable object can automatically generate text and values for the following controls:

  • asp:RadioButtonList
  • asp:CheckBoxList
  • asp:DropDownList
  • asp:Listbox

To bind data to a RadioButtonList control, first create a RadioButtonList control in a .aspx page (without any asp:ListItem elements)

<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server" AutoPostBack="True" />
</form>
</body>
</html>

Then add the script to build the list:

<script runat="server">
sub Page_Load
if Not Page.IsPostBack then
  dim mycountries=New Hashtable
  mycountries.Add("C","China")
  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 subroutine that will be executed when the user clicks on an item in the RadioButtonList control. When a radio button is clicked, a text will appear in the label:

<script runat="server">
sub Page_Load
if Not Page.IsPostBack then
  dim mycountries=New Hashtable
  mycountries.Add("C","China")
  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>

Display this example

Note:You cannot select the sorting method for adding items to the Hashtable. To sort items alphabetically or numerically, please use the SortedList object.