ASP.NET - The ArrayList Object

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The ArrayList object is a collection of items containing a single data value.

Create an ArrayList

The ArrayList object is a collection of items containing a single data value.

Items are added to the ArrayList with the Add() method.

The Below code creates a new ArrayList object named players and four items are added:

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim players=New ArrayList
  players.Add("Sachin")
  players.Add("Pointing")
  players.Add("Nadal")
  players.Add("Saina")
end if
end sub
</script>

By default, an ArrayList object contains 16 entries. An ArrayList can be sized to its final size with the TrimToSize() method:

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim players=New ArrayList
  players.Add("Sachin")
  players.Add("Pointing")
  players.Add("Nadal")
  players.Add("Saina")
  players.TrimToSize()
end if
end sub
</script>

An ArrayList can also be sorted alphabetically or numerically with the Sort() method:

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim players=New ArrayList
  players.Add("Sachin")
  players.Add("Pointing")
  players.Add("Nadal")
  players.Add("Saina")
  players.TrimToSize()
  players.Sort()
end if
end sub
</script>

To sort in reverse order, apply the Reverse() method after the Sort() method:

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim players=New ArrayList
  players.Add("Sachin")
  players.Add("Pointing")
  players.Add("Nadal")
  players.Add("Saina")
  players.TrimToSize()
  players.Sort()
  players.Reverse()
end if
end sub
</script>

Data Binding to an ArrayList

An ArrayList 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 .htmlx page:

<html>
<body>

<form runat="server">
<asp:RadioButtonList id="rb" runat="server" />
</form>

</body>
</html>

Then add the script that builds the list and binds the values in the list to the RadioButtonList control:

Example

<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
  dim players=New ArrayList
  players.Add("Sachin")
  players.Add("Pointing")
  players.Add("Nadal")
  players.Add("Saina")
  players.TrimToSize()
  players.Sort()
  rb.DataSource=players
  rb.DataBind()
end if
end sub
</script>

<html>
<body>

<form runat="server">
<asp:RadioButtonList id="rb" runat="server" />
</form>

</body>
</html>

The DataSource property of the RadioButtonList control is set to the ArrayList and it defines the data source of the RadioButtonList control. The DataBind() method of the RadioButtonList control binds the data source with the RadioButtonList control.

Note: The data values are used as both the Text and Value properties for the control. To add Values that are different from the Text, use either the Hashtable object or the SortedList object.


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