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Dim oList As ListItem For Each oList In oListBox.Items
If oList.Selected Then Do something
End If Next
6.3.1.7 The RadioButton control
The RadioButton control corresponds to a single button in a group of buttons used to indicate mutually exclusive choices. It has the following HTML syntax:
asp:RadioButton id=RadioButtonName AutoPostBack=True|False
Checked=True|False GroupName=GroupName
Text=label TextAlign=Right|Left
OnCheckedChanged=OnCheckedChangedMethod runat=server
As in the CheckBox control, the Checked
attribute determines whether the control is checked. Only one control in the group designated by
GroupName can be set to
True . The default value of the
Checked attribute is
False . However, since it is possible for the
Checked attributes of all radio
buttons in a group to be False
, it is important to initially set the Checked
attribute of one member of the group to
True . The
GroupName attribute provides a common name by which all radio buttons in
the group can be identified. The Text
attribute defines the caption that appears either to the left the default or to the right of the radio button, depending on the setting of the
TextAlign attribute.
Each of these attributes of the RadioButton control directly corresponds to an identically named property of the System.Web.UI.WebControls.RadioButton class. The value of the TextAlign property is
either of the two members of the TextAlign enumeration: TextAlign.Left
, which positions the text to the left of the checkbox the default; and
TextAlign.Right , which positions the text to the right
of the checkbox. The Checked property is a Boolean that can be programmatically set and can also change as a result of user interaction. Note that the user changing the Checked property of another
radio button in the group from False
to True
automatically changes the value of the Checked property of any checked radio button from
True to
False .
Finally, the OnCheckedChanged
attribute defines an event handler that will be executed whenever the Checked property of the radio button is changed. The event handler designated by the
OnCheckedChanged attribute must have the following signature:
Sub OnCheckedChangedMethodsender As Object, e As EventArgs
6.3.1.8 The Table control
The Table control corresponds to a table consisting of multiple rows, each having one or more columns. A table need not be symmetrical—that is, it need not have the same number of columns in
each row. The Table control has the following HTML syntax:
asp:Table id=TableName BackImageUrl=url
CellSpacing=cellspacing CellPadding=cellpadding
GridLines=None|Horizontal|Vertical|Both HorizontalAlign=Center|Justify|Left|NotSet|Right
runat=server
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asp:TableRow asp:TableCell
Cell text asp:TableCell
asp:TableRow asp:Table
The TableRow
tag defines a new table row, while the TableCell
tag defines a new cell within a particular row. The contents of the individual cell are defined by
Cell text . The
HorizontalAlign attribute determines the horizontal alignment of the table on the page. The
GridLines attribute
determines the appearance of grid lines in the table. The CellSpacing
attribute determines the number of pixels that separate individual cells of the table, while the
CellPadding attribute
determines the number of pixels between the cells border and its contents. The BackImageURL
attribute contains the URL of an image to be used as the background for the table. Each of these attributes corresponds to an identically named property of the Table class. The
CellPadding and CellSpacing properties are of type Integer. The value of the HorizontalAlign property is one of the following members of the HorizontalAlign enumeration:
Center ,
Justify ,
Left ,
NotSet , and
Right . The value of the GridLines property is one of the following members of the
GridLines enumeration: Both
, Horizontal
, None
, and Vertical
. You programmatically manipulate a table by manipulating its rows and its individual cells. The table
rows are accessible through the Table objects Rows property, which returns a TableRowCollection object containing TableRow objects that represent the rows of the table. The TableRowCollection
collection allows you to add rows to the end of the table by calling its Add method, which has the following syntax:
TableRowCollection.Add row
where row
is a TableRow object that represents a row of the table. To add a row to a particular place in the table, you can call the Insert method, which has the following syntax:
TableRowCollection.Insertindex, row where
index is the zero-based position in the table at which the row is to be added and
row is a
RowTable object representing the row to be added to the table. You can also remove rows from the table by calling the TableRowCollection objects Remove and RemoveAt methods. The syntax of the
Remove method is:
TableRowCollection.Removerow where
row is a TableRow object representing the row to be deleted. The syntax of the RemoveAt
method is: TableRowCollection.RemoveAtindex
where index
is the position of the row to be removed from the table. The number of items in the table is provided by the TableRowCollection objects Count property. Individual TableRow objects
representing individual rows of the table can be retrieved using the Item property, whose syntax is: TableRowCollection.Itemindex
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where index
is the zero-based ordinal position of the row whose TableRow object you wish to retrieve.
Once youve retrieved a reference to an individual table row, you can use its Cells property to retrieve a reference to a TableCellCollection object, which contains a collection of TableCell objects
representing the individual cells of the row. Like the TableRowCollection class, the TableCellCollection class has members to add and remove individual cells as well as to determine how many cells are in
the collection. Its syntax for adding and removing cells is identical to that of the TableRowCollection class, except that TableCell objects are used instead of TableRow objects. Finally, to retrieve an
individual cell, you use the TableCellCollection objects Item method, which has the following syntax:
TableCellCollection.Itemindex where
index is the zero-based ordinal position of the cell in the row. The property returns a TableCell
object representing the cell. Finally, the TableCell class has a number of properties that control the content and appearance of the
cell. The Text property determines the cells content. The Boolean Wrap property determines whether the contents of the cell wrap in the cell; its default value is
True . The RowSpan and ColumnSpan
properties are Integer values that indicate how many table rows and how many table columns the cell spans. The HorizontalAlign property, whose value is a member of the HorizontalAlign enumeration
discussed earlier in this section, determines the horizontal alignment of the cells contents. The VerticalAlign property determines the vertical alignment of the cells contents. Its value must be a
member of the VerticalAlign enumeration, which has the following members:
Bottom ,
Middle ,
NotSet , and
Top .
6.3.1.9 The TextBox control