ASP.NET - The ArrayList Object
The ArrayList object is a collection of items containing a
single data value.
Examples
Example 1 - ArrayList RadioButtonList
Example 2 - ArrayList DropDownList
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 following code creates a new ArrayList object named
mycountries and four items are added:
<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
dim mycountries=New ArrayList
mycountries.Add("Norway")
mycountries.Add("Sweden")
mycountries.Add("France")
mycountries.Add("Italy")
end if
end sub
</script>
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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 mycountries=New ArrayList
mycountries.Add("Norway")
mycountries.Add("Sweden")
mycountries.Add("France")
mycountries.Add("Italy")
mycountries.TrimToSize()
end if
end sub
</script>
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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 mycountries=New ArrayList
mycountries.Add("Norway")
mycountries.Add("Sweden")
mycountries.Add("France")
mycountries.Add("Italy")
mycountries.TrimToSize()
mycountries.Sort()
end if
end sub
</script>
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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 mycountries=New ArrayList
mycountries.Add("Norway")
mycountries.Add("Sweden")
mycountries.Add("France")
mycountries.Add("Italy")
mycountries.TrimToSize()
mycountries.Sort()
mycountries.Reverse()
end if
end sub
</script>
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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 .aspx page:
<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server" />
</form>
</body>
</html>
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Then add the script that builds the list and binds the values
in the list to the RadioButtonList control:
<script runat="server">
Sub Page_Load
if Not Page.IsPostBack then
dim mycountries=New ArrayList
mycountries.Add("Norway")
mycountries.Add("Sweden")
mycountries.Add("France")
mycountries.Add("Italy")
mycountries.TrimToSize()
mycountries.Sort()
rb.DataSource=mycountries
rb.DataBind()
end if
end sub
</script>
<html>
<body>
<form runat="server">
<asp:RadioButtonList id="rb" runat="server" />
</form>
</body>
</html>
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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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