Web Forms Hashtable
ASP.NET Web Forms - Hashtable Object
The Hashtable object contains items represented by key/value pairs.
Try it - Example
Hashtable RadiobuttonList 1
Hashtable RadiobuttonList 2
Hashtable DropDownList
Creating a Hashtable
A Hashtable object contains items represented by key/value pairs. The key is used as an index, and by searching for the key, a quick search of the value can be achieved.
Add items to the Hashtable through the Add() method.
The following code creates a Hashtable object named mycountries and adds four elements:
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
Hashtable objects can automatically generate text and values for the following controls:
- asp:RadioButtonList
- asp:CheckBoxList
- asp:DropDownList
- asp:Listbox
In order to bind data to the RadioButtonList control, first create a RadioButtonList control in the .aspx page (without any asp:ListItem elements):
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server" AutoPostBack="True" />
</form>
</body>
</html>
Then add the script that creates the list and bind the values in the list to the RadioButtonList control:
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 subexample This subroutine will be executed when the user clicks an item in the RadioButtonList control. When a radio button is clicked, a line of text will appear in the label:
Instance
<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>
<!DOCTYPE html>
<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>Run Example»
Click the "Run Instance" button to view the online instance
Note: You cannot choose how items added to the Hashtable are sorted. To sort items alphabetically or numerically, use a SortedList object.
