ASP.NET - SortedList object

The SortedList object has the characteristics of both ArrayList and Hashtable objects.

Instance

SortedList RadiobuttonList 1
SortedList RadiobuttonList 2
SortedList DropDownList

SortedList object

The SortedList object contains items represented by key/value pairs. The SortedList object can automatically sort the items in alphabetical or numerical order.

Items are added to the SortedList through the Add() method. The SortedList can be adjusted to the final size with the TrimToSize() method.

The following code creates a SortedList named mycountries and adds four elements:

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

Data binding

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

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

To bind data to the RadioButtonList control, first create a RadioButtonList control in the aspx file (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 SortedList
  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 the radio button is clicked, the text will appear in the label:

<script runat="server">
sub Page_Load
if Not Page.IsPostBack then
  dim mycountries=New SortedList
  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>

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