C# Programming: From Problem Analysis to Program Design, 2nd ed.
Chapter 8
Introduction to Windows Programming
At a Glance
Instructor’s Manual Table of Contents
♦ Chapter Overview
♦ Chapter Objectives
♦ Instructor Notes
♦ Quick Quizzes
♦ Discussion Questions
♦ Projects to Assign
♦ Key Terms
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Lecture Notes
Chapter Overview
In this chapter, students extend their knowledge of programming by creating applications that
capture and respond to user input. A different way of programming based on interactively
responding to events such as mouse clicks is introduced. Windows-based applications using the
.NET Framework Class Library are built. Classes that enable highly interactive, attractive,
graphical user interface (GUI) applications are introduced. The drag-and-drop construction
approach available with Visual Studio is illustrated.
Chapter Objectives
In this chapter, students will:
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Differentiate between the functions of Windows applications and console applications
Learn about graphical user interfaces
Become aware of some elements of good design
Use C# and Visual Studio to create Windows-based applications
Create Windows forms and be able to change form properties
Add control objects such as buttons, labels, and text boxes to a form
Work through a programming example that illustrates the chapter’s concepts
Instructor Notes
CONTRASTING WINDOWS AND CONSOLE APPLICATIONS
With a console-based application, each line in the Main ( ) method is executed sequentially.
Then the program halts. Method calls might branch to different locations in your program;
however, control always returns to Main ( ). Programs retrieve data by calling the operating
system to get data, and they call on the operating system to output data through method calls
such as WriteLine( ) or Write( ).
Once launched, the Windows application sits in a process loop waiting for an event—
notification from the operating system that an action, such as the user clicking the mouse or
pressing a key, has occurred. Instead of calling on the operating system with a request, as
console applications do, Windows applications receive messages from the operating system that
an event has occurred. Methods called event handlers indicate what should be done when an
event occurs.
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Both console and Windows applications begin execution in the Main ( ) method. However,
unlike console-based applications that exit after all statements have been sequentially executed,
Windows-based applications, once they are launched, sit idly waiting for notification of a
registered event. These event-handler methods may be executed in a different order every time
your application runs. The program remains in the operating system environment in the process
loop. This means your program could be minimized, resized, or closed like other Windows
applications.
Windows applications not only function differently, they also look different.
Quick Quiz
1. True or False: Windows applications do not have a Main ( ) method.
Answer: False
2. Special methods called ________ _________ are written to indicate what should happen
when an event such as a mouse click occurs.
Answer: event handlers
3. When a Windows application is executed, it sits in a ________ ____________.
Answer: process loop
4. True or False: Windows applications also look different than console-based applications.
Answer: True
GRAPHICAL USER INTERFACES
Program interaction with console-based applications have been limited to accepting input
through the ReadLine ( ) method and displaying output at the DOS console window. The
interfaces were not graphical. Windows applications include a graphical user interface (GUI). A
graphical user interface (GUI) can include menus, buttons, pictures, and text in many different
colors and sizes. These controls can display and respond to user interaction. The form is a
container waiting to hold additional controls. Forms have a title bar, complete with an icon on
the left, a textual caption in the title bar, and the typical Windows minimize, maximize, and
close buttons. Visual Studio Integrated Development Environment (IDE) automatically
generates all the code needed for a blank Windows form. Use the built-in, drag-and-drop
construction of the IDE to add the controls.
Most of the classes for developing Windows-based application are organized in the
System.Windows.Forms namespace. Use the using directive to import types or classes from the
System.Windows.Forms namespace. Visual Studio automatically adds this reference and
imports the namespace when you create a Windows Application Project using the IDE.
The class heading definition includes the class name and a colon followed by another class
name. The second class is called the base class; the first is called the derived class.
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The heading added is:
public class Form1 : Form
The new class inherits all the functionality of the base class. Form is a predefined .NET class
that includes a number of methods and properties used to create a basic Windows screen.
Windows forms and controls offer a wide variety of changeable properties including Text,
Color, Font, Size, and Location. Much of the power of Visual Studio lies in having these
properties readily available and easy to change or add through IntelliSense. Text is a property
that can be used to set or get the caption of the title bar for the window.
Execution for Windows-based programs begins in the Main( ) method. First statement
instantiates or creates an object of the Form1 class (Form1 winForm = new Form1( );). Last
statement in the body of Main( ) calls the Run( ) method (Application.Run(winForm);).
Application class is also defined as part of the System.Windows.Forms namespace. The object
that is instantiated from the Form1 class is sent as the argument to its Run( ) method. This
Run( ) method call is what displays the form and places the application in a process loop so that
it receives messages from the operating system when events of interest to the application are
fired. The Exit( ) method stops an application and closes all of its windows.
Quick Quiz
1. What statement places a Windows application in the process loop?
Answer: Application.Run(formName);
2. True or False: In a class heading such as "public class Form1 : Form", Form1 is the derived
class.
Answer: True
3. Identify two Form properties that can be changed.
Answer: Text and Font
4. Give three examples of Control objects.
Answer: Button, Menu, Label
ELEMENTS OF GOOD DESIGN
Appearance matters! The goal should be to develop applications that are usable, that permit
users to spot items in the windows quickly, and that enable users to interact with your program.
A large field of research, called human-computer interaction (HCI), concentrates on the design
and implementation of interactive computing systems for human use. Few HCI considerations
include design consideration in the area of consistency, alignment, avoid clutter, color, and the
target audience.
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Consistency
Consistent placement of items is important. Consistent sizing of items is important. Consistent
appearance of items that are performing the same functionality is also important. Unless you
are trying to call attention to an item, keep the item the same as other items. Use contrast to
bring attention.
Alignment
Use alignment for grouping items. When you place controls on a form, place similar items
together. They can be lined up to call attention to the fact that they belong together.
Avoid Clutter
Do not crowd a form with too many controls. Fonts should be large enough to be legible.
Color
Background colors and foreground text colors should contrast each other. Avoid using bright
colors (such as reds), especially for backgrounds—this can result in user eye fatigue. You can
use color as an attention getter, but do not abuse it. Color can play a significant role in your
design.
Target Audience
Think about the design of an interface in terms of who will be using it and on what platform it
will be displayed.
Quick Quiz
1. True or False: Always try to include as many controls on the form as you can place.
Answer: False
2. True or False: Use bright colors on the form to call attention to the controls.
Answer: False
3. True or False: Forms should include a maximum of three controls per container.
Answer: False
4. Identify three issues that should be taken into consideration when you design a form.
Answer: Avoid clutter, think about the intended audience, and be consistent with the
placement of controls on the form
USE C# AND VISUAL STUDIO TO CREATE WINDOWS-BASED
APPLICATIONS
Visual Studio automatically generates code when you create a Windows application. Begin by
selecting File>New>Project and selecting Visual C# Project as the Project Type with Windows
Application selected from the list of Templates. Browse to the location where you want to
store your work. Use the View menu to display different windows, such as the Toolbox,
Solution Explorer, Class View, Properties, and Dynamic Help windows.
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Experiment with the pushpin icon on the title bar of specific windows. The Auto Hide feature
minimizes that window.
Quick Quiz
1. Which template do you select for the project type if you plan to design an application that
shows a windows form on the screen?
Answer: Windows Application
2. The ________ icon can be used to minimize the window and place a tab for it in the current
workspace.
Answer: pushpin
3. True or False: Visual Studio will generate much of the code for you to create a Windows
form.
Answer: True
4. List three specific windows that can be opened in the workspace when a Windows
application is being created.
Answer: Class, Solutions Explorer, Dynamic Help
WINDOWS FORMS
The top-level window for an application is called a “form”. There is an extensive collection of
Control classes including a Form class, which is used as a container to hold other controls.
Windows Form Properties
The Properties window is used to view and change the design time properties and events of an
object. In the Properties window, properties that have a plus symbol (+) to the left of the
property name indicate that the property can be expanded. Groups of properties are collapsed
together for easier navigation. Use intuitive names for most of the properties.
Beginning with Visual Studio 2005, the IDE separates the source code into three files when you
create a simple Windows application. Initially, these files are named Form1.cs,
Form1.Designer.cs and Program.cs. The first two files, Form1.cs and Form1.Designer.cs, both
include partial class definitions for the Form1 class. It is recommended that you never edit the
Form1.Designer.cs file. You will normally only be editing the Form1.cs file. The Program.cs
file contains the Main( ) method, where execution always begins.
Inspecting the Code Generated by Visual Studio
#region is one of the preprocessor directives used to mark sections of code that can be expanded
or collapsed. Visual Studio adds a region labeled “Windows Form Designer generated code”.
Clicking (+) expands the listing. There is also a #endregion.
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Comparing the Code of Example 8-1 to Example 8-2
Visual Studio uses a method named InitializeComponent ( ) to build the form at run time. The
call to this method is the only statement in the constructor. All code setting the properties that
are set during design are placed in InitializeComponent ( ) method.
Each of the properties are suffixed with the keyword this, referring to the current instance of a
class. In the call to the Run ( ) method ( Application.Run(new Form1( )); ), no identifier is
associated with the Form1 object. The new keyword creates an anonymous (unnamed) instance
of Form1. The Form1 object identifier is not used anywhere else. Thus, there is no reason to
name it.
The Dispose ( ) is added by Visual Studio to perform memory management. The automatic
garbage collector releases memory from the application after the program is halted. It cleans up
or releases unused resources back to the operating system.
Windows Form Events
The topic of Chapter 9 is handling events. One way to add a method to handle events in Visual
Studio is to find the event in the list of events (from the Properties window with the lightning
bolt (Events) ) and double-click on the event name. Code is automatically added to the program.
In the InitializeComponent ( ) method, the event is registered as being of interest using a
statement similar to:
this.FormClosing +=
new System.Windows.Forms.FormClosingEventHandler
(this.Form1_FormClosing);
The above statement registers the program to be notified when a user is closing the application.
In addition, an event-handler method heading and an empty body is added to the code as shown
here:
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
}
Quick Quiz
1. The top-level control onto which all others controls are added is called a _________ in a
Windows application.
Answer: form
2. True or False: When you are using Visual Studio to create a Windows application, you
must type a using directive that reads using System.Windows.Forms;.
Answer: False
3. True or False: Visual Studio inserts #region …#endregion preprocessor directive with a
label of Windows Form Designer generated code.
Answer: True
4. When does the Dispose( ) method do?
Answer: It releases memory from the application after the program is halted.
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CONTROLS
System.Windows.Forms namespace includes controls with names such as Button, Label,
TextBox, ComboBox, MainMenu, ListBox, CheckBox, RadioButton, and MonthCalendar. Each
of these controls are classes with properties and methods. Each fires events—some of which you
should write methods for—indicating what to do when its event is fired. A lot of code is added
automatically for you when you place the control on the form.
All of the control classes that can be added to a form are derived from the
System.Windows.Forms.Control class, which means they inherit the characteristics of the
Control class. Call attention to Figure 8-8 and 8-9. They show the controls that can be added.
Place, Move, Resize, and Delete Control Objects
Either double-click the control or drag and drop the control to the correct location on the form to
place it. Resize controls using the standard Windows conventions of positioning the mouse
pointer over the resizing handles. Clicking the Delete or Backspace key, once the control is
selected, removes the control visually from the Form Designer view, but also removes all the
constructor code and associated property changes relating to the selected object.
With the release of Visual Studio 2005, the Windows Forms Designer has a SnapLine feature to
help you accomplish precise layout of controls on your form. Horizontal and vertical line
segments are dynamically created by the SnapLine feature to assist in the layout of controls.
Options under the Format menu including Align, Make Same Size, Horizontal Spacing, and
Vertical Spacing should be explored. After the controls are selected, use, for example, Align to
align lefts, rights, or centers of controls. The Make Same Size selection is useful for sizing
objects for consistency. Note that when you select more than one control to format, the last
control selected is the one used as the template for the action. The Horizontal and Vertical
Spacing options enable you to increase or decrease the amount of blank space displayed
between objects.
Methods and Properties of the Control Class
Call attention to Table 8-2 for a list of Control properties inherited by control objects such as
buttons and labels. Table 8-3 includes a list of the control methods. Some of the methods
provide the same functionality as one or more of the properties. For example, the Show ( )
method functions the same way as setting the Visible property to true; Hide( ) does the same
thing as setting the Visible property to false.
Derived Classes of the System.Windows.Form.Control Class
Figure 8-11 shows a visual representation of many of the controls you add to a form. They are
labeled.
• Label—used to provide descriptive text for another control. Can also be used to display
information at run time. A number of properties can be set including Text, TextAlign,
Visible, Font, and Location.
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TextBox—used to enter data or display text during run time. Probably the most
commonly used control because it can be used for both input and output. Text property
is used to get or set the string value in the control. Other properties that are of interest
include: MultiLine, ScrollBars, MaxLength, PasswordChar, and CharacterCasing. Table
8-6 describes these properties. Methods, including AppendText ( ), which adds text to
the end of the current text of the TextBox and Clear( ), can be used with TextBox
objects.
Button—Objects that increase functionality. They enable a user to click a button to
perform a specific task. When it is clicked by a user, the event-handler method is
automatically called up—if the button has an event-handler method—and is registered as
an event to which your program is planning to respond. Button objects have a number of
properties, methods, and events. They also inherit the properties, methods, and events
from the Control class. Specific properties and methods of interest include Enabled,
Focused, Focus( ), AcceptButton, and Name.
TabIndex, inherited from Control, is useful for setting or getting the tab order of the controls
on a form. By default, the tab order is the same order as the order of how the controls are
added to the form. You can change this order when you are in View Tab Order by clicking
the controls sequentially to establish the new order.
Add a Click event to an object, such as a button, by double-clicking on the object in the
Form Designer. When you add the event this way, the default event is registered and the
method heading along with the empty body for the method is added. All that is required is
for the programmer to write the program statements that should be executed when the event
is fired. Another way to register an event is to select the event from the Properties window
after clicking the Events icon.
Quick Quiz
1. True or False: Once controls, such as buttons or text boxes are added to a form, they can be
resized, moved, or deleted using the standard Windows conventions.
Answer: True
2. True or False: The Button class is derived from the Form class.
Answer: False
3. The control that is probably used more often than other controls for both input and output is
the ______.
Answer: TextBox
4. The property that is used with most controls to set the caption for the control is the _______
property.
Answer: Text
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PROGRAMMING EXAMPLE: TempAgency Application
This application is created to demonstrate the design and implementation of a graphical user
interface for a Windows application. An application for a TempAgency is designed that accepts
as input the contractor’s name, number of dependents, and the number of hours worked. It
displays the gross pay, deductions, and the net pay for the worker.
Two classes are constructed to separate the business logic from the presentation details. The
Employee class defines a template for a typical payroll employee object. It includes the
behaviors for determining withholding deductions and calculating the net take-home pay. The
second-class instantiates objects of the .NET predefined Control classes (labels, text boxes, and
button) and adds those objects to the Form object.
Structured English (pseudocode) and class diagrams are included with the example. A prototype
for the desired output is shown. Tables are shown documenting the properties that were set
during design. The complete program listing is shown in the book and available as a Visual
Studio project to demo for the class.
Discussion Questions
Some interesting topics of discussion in this chapter include:
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Select a Windows application, such as a game or productivity package, and analyze the
user interface in terms of the design considerations included in this chapter.
Compare and contrast a typical Windows application to a console-based application.
Why can a Windows application take twice as much time to develop as a console-based
application?
Projects to Assign
All of the Multiple Choice Exercises, Problems 1-20
Odd numbered Short Answer Exercises, Problems 21-25
Programming Exercises, Problems 3, 5, 9, and 10
Key Terms
¾ controls: objects that can display and respond to user interaction
¾ derived class: new class that that inherits the characteristics of the base class
¾ event: a notification from the operating system that an action, such as the user clicking
the mouse or pressing a key, has occurred
¾ event handlers: methods that indicate what should be done when an event such as a
mouse click on a button or the press of a key occurs
¾ graphical user interface (GUI): the menus, buttons, pictures, and text front end
portion of the program
¾ Human-Computer Interaction (HCI): design and implementation of interactive
computing systems for human use
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¾ interface: the front end of a program—the visual image you see when you run a
program
¾ preprocessor directive: directive indicating what should be done prior to processing
the program statements
¾ Windows applications: applications that are usually graphical and that use the event
model and receive messages from the operating system that an event has occurred