Introduction & Demonstration
The ListBox control is similar to the DropDownList control with two important
differences. First, the ListBox control requires more screen real estate because
it always displays a certain number of list items. Furthermore, unlike the
DropDownList control, the ListBox control enables a user to select multiple
items.
Selecting Single Item
The page given below illustrates how we can enable a user to select a single
item from a ListBox control.
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD
XHTML 1.0
Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As EventArgs)
lblProduct.Text = lstProducts.SelectedItem.Text
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ListBox
id="lstProducts"
DataSourceID="SqlDataSource1"
DataTextField="TITLE"
DataValueField="ID"
Rows="4"
Runat="server" />
<p>
<asp:Button
id="btnSubmit"
Text="Submit"
OnClick="btnSubmit_Click"
Runat="server" />
</p>
<hr />
<asp:Label
id="lblProduct"
Runat="server" />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$
ConnectionStrings:DatabaseConnectionString1 %>"
ProviderName="<%$
ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
SelectCommand="SELECT
[ID], [TITLE] FROM [PRO_LIST]"></asp:SqlDataSource>
</div>
</form>
</body>
</html>
Notice that the ListBox control in above example includes a Rows property. The
Rows property determines the number of list items that the ListBox displays.
Selecting Multiple Item
We can also configure the ListBox control to enable a user to select multiple
items. This is illustrated in the page given below.
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD
XHTML 1.0
Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As EventArgs)
For Each item As ListItem In lstProducts.Items
If item.Selected Then
lblProduct.Text &= "<li>" &
item.Text
End If
Next
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ListBox
id="lstProducts"
DataSourceID="SqlDataSource1"
DataTextField="TITLE"
DataValueField="ID"
Rows="4"
SelectionMode="multiple"
Runat="server" />
<p>
<asp:Button
id="btnSubmit"
Text="Submit"
OnClick="btnSubmit_Click"
Runat="server" />
</p>
<hr />
<asp:Label
id="lblProduct"
EnableViewState="false"
Runat="server" />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$
ConnectionStrings:DatabaseConnectionString1 %>"
ProviderName="<%$
ConnectionStrings:DatabaseConnectionString1.ProviderName %>"
SelectCommand="SELECT
[ID], [TITLE] FROM [PRO_LIST]"></asp:SqlDataSource>
</div>
</form>
</body>
</html>
Notice that the ListBox given above includes a SelectionMode property that is
set to the value Multiple. A user can select multiple items from the ListBox by
using the Ctrl or Shift key when clicking more than one list item. Most users
don't understand how to select multiple items from a ListBox control. If you
want to enable users to pick multiple items, a better approach is to use either
the CheckBoxList control or the MultiSelectList control. When we click the
Submit button then all the selected list items are displayed in a Label control.
The SelectedItem, SelectedIndex, and SelectedValue properties return only the
first list item selected. When multiple items are selected, we need to iterate
through the Items collection of the ListBox control to detect the selected
items.
HAVE A GREAT CODING!
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