ASP.NET 4 Unleased - p 50 ppt

When you click the Submit button in Listing 10.12, all the selected list items display in a Label control.. Working with the CheckBoxList Control The CheckBoxList control renders a list

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CHAPTER 10 Using List Controls

LISTING 10.11 ShowListBox.aspx

<%@ Page Language=”C#” %>

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.1//EN”

“http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd”>

protected void btnSubmit_Click(object sender, EventArgs e)

{

lblMovie.Text = lstMovies.SelectedItem.Text;

}

</script>

<title>Show ListBox</title>

</head>

<body>

<div>

<asp:ListBox

id=”lstMovies”

DataSourceID=”srcMovies”

DataTextField=”Title”

DataValueField=”Id”

Rows=”8”

Runat=”server” />

<p>

<asp:Button

id=”btnSubmit”

Text=”Submit”

OnClick=”btnSubmit_Click”

</p>

<hr />

<asp:Label

id=”lblMovie”

<asp:SqlDataSource

id=”srcMovies”

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SelectCommand=”SELECT Id, Title FROM Movies”

ConnectionString=”<%$ ConnectionStrings:Movies %>”

</div>

</form>

</body>

</html>

The ListBox control in Listing 10.11 includes a Rows property The Rows property

deter-mines the number of list items that the ListBox displays

You can also configure the ListBox control to enable a user to select multiple items This

is illustrated in the page in Listing 10.12 (see Figure 10.11)

FIGURE 10.11 Selecting multiple list items

LISTING 10.12 ShowMultipleListBox.aspx

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{

foreach (ListItem item in lstMovies.Items)

if (item.Selected)

lblMovie.Text += “<li>” + item.Text;

}

</script>

<title>Show Multiple ListBox</title>

</head>

<body>

<div>

<asp:ListBox

id=”lstMovies”

SelectionMode=”Multiple”

<p>

<asp:Button

id=”btnSubmit”

Text=”Submit”

</p>

<hr />

<asp:Label

id=”lblMovie”

EnableViewState=”false”

<asp:SqlDataSource

id=”srcMovies”

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</div>

</form>

</body>

</html>

The ListBox in Listing 10.12 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

WARNING

Most users don’t understand how to select multiple items from a ListBox control If

you want to allow users to pick multiple items, a better approach is to use either the

CheckBoxList control (discussed in the next section) or the MultiSelectList control

(discussed in the final section)

When you click the Submit button in Listing 10.12, all the selected list items display in a

Label control The SelectedItem, SelectedIndex, and SelectedValue properties return

only the first list item selected When multiple items are selected, you need to iterate

through the Items collection of the ListBox control to detect the selected items

Working with the CheckBoxList Control

The CheckBoxList control renders a list of check boxes, which can be rendered

horizon-tally or vertically Unlike the other List controls, a user always can select multiple items

when using a CheckBoxList control

For example, the page in Listing 10.13 contains a CheckBoxList control that renders its list

items in two columns (see Figure 10.12)

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ptg CHAPTER 10 Using List Controls

LISTING 10.13 ShowCheckBoxList.aspx

{

foreach (ListItem item in cblMovies.Items)

if (item.Selected)

lblMovie.Text += “<li>” + item.Text;

}

</script>

<title>Show CheckBoxList</title>

</head>

<body>

<div>

FIGURE 10.12 Displaying list items with the CheckBoxList control

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<asp:CheckBoxList

id=”cblMovies”

RepeatColumns=”2”

<p>

<asp:Button

id=”btnSubmit”

Text=”Submit”

</p>

<hr />

<asp:Label

id=”lblMovie”

EnableViewState=”false”

<asp:SqlDataSource

id=”srcMovies”

</div>

</form>

</body>

</html>

When you click the Submit button, the values of the Text property of any selected check

boxes display in a Label control The selected check boxes are retrieved from the

CheckBoxList control’s Items property

The CheckBoxList control includes three properties that affect its layout:

RepeatColumns—The number of columns of check boxes to display

RepeatDirection—The direction in which the check boxes are rendered Possible

values are Horizontal and Vertical

RepeatLayout—Determines whether the check boxes display in an HTML table

Possible values are Table and Flow

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Normally, a CheckBoxList control renders its list items in an HTML table When the

RepeatLayout property is set to the value Flow, the items are not rendered in a table

Working with the BulletedList Control

The BulletedList control renders either an unordered (bulleted) or ordered (numbered)

list Each list item can be rendered as plain text, a LinkButton control, or a link to another

web page

For example, the page in Listing 10.14 uses the BulletedList control to render an

unordered list of movies (see Figure 10.13)

FIGURE 10.13 Displaying a list items with the BulletedList control

LISTING 10.14 ShowBulletedList.aspx

<title>Show BulletedList</title>

</head>

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<body>

<div>

<asp:BulletedList

id=”blMovies”

<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”SELECT Title FROM Movies”

</div>

</form>

</body>

</html>

You can control the appearance of the bullets that appear for each list item with the

BulletStyle property This property accepts the following values:

Circle

CustomImage

Disc

LowerAlpha

LowerRoman

NotSet

Numbered

Square

UpperAlpha

UpperRoman

You can set BulletStyle to Numbered to display a numbered list If you set this property

to the value CustomImage and assign an image path to the BulletImageUrl property, you

can associate an image with each list item For example, the page in Listing 10.15

displays an image named Bullet.gif with each list item (see Figure 10.14)

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ptg CHAPTER 10 Using List Controls

LISTING 10.15 ShowBulletedListImage.aspx

<title>Show BulletedList Image</title>

</head>

<body>

<div>

<asp:BulletedList

id=”blMovies”

BulletStyle=”CustomImage”

BulletImageUrl=”~/Images/Bullet.gif”

FIGURE 10.14 Displaying image bullets

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<asp:SqlDataSource

id=”srcMovies”

SelectCommand=”SELECT Title FROM Movies”

</div>

</form>

</body>

</html>

You can modify the appearance of each list item by modifying the value of the

DisplayMode property This property accepts one of the following values from the

BulletedListDisplayMode enumeration:

HyperLink—Each list item renders as a link to another page

LinkButton—Each list item renders by a LinkButton control

Text—Each list item renders as plain text

For example, the page in Listing 10.16 displays a list of links to other websites (see

Figure 10.15)

FIGURE 10.15 Displaying list items as hyperlinks

Tiêu đề	Using List Controls
Trường học	University of Wow!
Chuyên ngành	Computer Science
Thể loại	Essay
Năm xuất bản	2025
Thành phố	Wow City

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