CreateSites: ASP.NET - The SortedList Object

Tuesday, July 5, 2011

ASP.NET - The SortedList Object

The SortedList Object

The SortedList object contains items in key/value pairs. A SortedList object automatically sort the items in alphabetic or numeric order.
Items are added to the SortedList with the Add() method. A SortedList can be sized to its final size with the TrimToSize() method.
The following code creates a SortedList named mycountries and four elements are added:

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

Data Binding

A SortedList 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 SortedList
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 SortedList
  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>

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