Visual Basic.NET How to Program (PDF)

534 Graphical User Interfaces Concepts: Part 2 Chapter 13
a manner similar to that of the event handlers for the Color menu items. Each event handler
clears the Checked properties for all font-type menu items by calling method ClearFont
(lines 118–124), then sets the Checked property of the menu item that raised the event to
True. This enforces the mutual exclusion of the font-type menu items.
The event handlers for the Bold and Italic menu items (lines 166–191) use the bitwise
Xor operator. For each font style, the Xor operator changes the text to include the style or,
if that style is already applied, to remove it. The toggling behavior provided by the Xor
operator is explained in Chapter 12, Graphical User Interfaces Concepts: Part 1. As
explained in Chapter 12, this program’s event-handling structure allows the programmer to
add and remove menu entries while making minimal structural changes to the code.
13.3 LinkLabels
The LinkLabel control displays links to other resources, such as files or Web pages
(Fig. 13.6). A LinkLabel appears as underlined text (colored blue by default). When the
mouse moves over the link, the pointer changes to a hand; this is similar to the behavior of
a hyperlink in a Web page. The link can change color to indicate whether the link is new,
previously visited or active. When clicked, the LinkLabel generates a LinkClicked
event (see Fig. 13.7). Class LinkLabel is derived from class Label and therefore inherits
all of class Label’s functionality.
Look-and-Feel Observation 13.5
Although other controls can perform actions similar to those of a LinkLabel (such as the
opening of a Web page), LinkLabels indicate that a link can be followed—a regular label
or button does not necessarily convey that idea. 13.5
LinkLabel
on a form Hand image displays when
mouse moves over LinkLabel
Fig. 13.6 LinkLabel control in running program.
LinkLabel
properties and events Description / Delegate and Event Arguments
Common Properties
ActiveLinkColor Specifies the color of the active link when clicked. Red is the default.
LinkArea Specifies which portion of text in the LinkLabel is part of the link.
Fig. 13.7 LinkLabel properties and events (part 1 of 2).