Programming ASP .NET

Selecting Values

Several ASP controls allow the user to select a value or values:

CheckBox

Allows selection of Boolean data

RadioButton

Allows only a single option to be selected

CheckBoxList

Group of CheckBox controls that can be dynamically created and bound to a data source

RadioButtonList

Group of RadioButton controls that can be dynamically created and bound to a data source

ListBox

Allows selection of one or more items from a predefined list

DropDownList

Similar to a ListBox, but allows only a single selection

All of these controls derive from the WebControl class. The RadioButton derives further from the CheckBox class, and the last four controls, the List controls, all derive from the abstract ListControl class. Each of these controls is considered in detail in the upcoming sections.

CheckBox Control

A CheckBox control provides a means for a user to select Boolean data (i.e., Yes/No or True/False). If you have several checkboxes arranged together (not to be confused with a CheckBoxList), then you can select multiple options. No option is mutually exclusive of another.

The C# code in Example 5-10 shows the use of three independent CheckBoxes to control the appearance of a Label. (The equivalent VB.NET code, which is nearly identical to the C# code, is shown in Example 5-11.) Clicking on any of the checkboxes in these examples -- Underline, Overline, or Strikeout -- imposes that attribute on the text string in the Label control. The results of the C# code are shown in Figure ...