1. Chapter 12 - Graphical User Interface Concepts: Part 1
Outline Introduction Windows Forms Event-Handling Model Basic Event Handling Control Properties and Layout Labels, TextBoxes and Buttons GroupBoxes and Panels CheckBoxes and RadioButtons PictureBoxes Mouse Event Handling Keyboard Event Handling

2. Graphical user interface
12.1 Introduction
Graphical user interface
Allow interaction with program visually
Give program distinct look and feel
Built from window gadgets
Is an object, accessed via keyboard or mouse

3. 12.1 Introduction
Button
Label
Menu Bar
TextBox
Scrollbar
Fig Sample Internet Explorer window with GUI components.

4. 12.1 Introduction

5. 12.2 Windows Forms WinForms Create GUIs for programs
Element on the desktop
Represented by:
Dialog
Window
MDI window

6. 12.2 Windows Forms Component Control Event
Class that implements IComponent interface
Lacks visual parts
Control
Component with graphical part
Such as button or label
Are visible
Event
Generated by movement from mouse or keyboard
Event handlers performs action
Specifics written by programmer

7. 12.2 Windows Forms
Fig Components and controls for Windows Forms.

8. 12.2 Windows Forms

9. 12.3 Event-Handling Model GUIs are event driven Event handlers
Methods that process events and perform tasks.
Associated delegate
Objects that reference methods
Contain lists of method references
Must have same signature
Intermediaries for objects and methods
Signature for control’s event handler

10. 12.3 Event-Handling Model Object A raises event E Delegate for event E
Handler 1 for event E
Handler 3 for event E
Handler 2 for event E
calls
Fig Event-handling model using delegates.

11. 12.3.1 Basic Event Handling Event handler Event multicasting
Must have same signature as corresponding delegate
Two object reference are passed in
ControlName_EventName
Must be registered with delegate object
Add event handlers to the delegate’s invocation list
New delegate object for each event handler
Event multicasting
Have multiple handlers for one event
Order called for event handlers is indeterminate

12. 12.3.1 Basic Event Handling Events icon
List of events supported by control
Selected event
Current even handler (none)
Event description
Fig Events section of the Properties window.

13. Class EventArgs is base class for objects with event information
1 // Fig. 12.7: SimpleEventExample.cs
2 // Using Visual Studio .NET to create event handlers. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 // program that shows a simple event handler
12 public class MyForm : System.Windows.Forms.Form
13 {
private System.ComponentModel.Container components = null; 15
// Visual Studio .NET generated code 17
[STAThread]
static void Main() {
Application.Run( new MyForm() ); } 23
// Visual Studio .NET creates an empty handler,
// we write definition: show message box when form clicked
private void MyForm_Click( object sender, System.EventArgs e ) {
MessageBox.Show( "Form was pressed" ); } 30
31 } // end class MyForm
SimpleEventExample.cs
Class EventArgs is base class for objects with event information
Create an event handler
Reference to the object that raised the event (sender)
Signature of the event handler
Reference to an event arguments object (e)

14. SimpleEventExample.cs Program Output

15. 12.3.1 Basic Event Handling Class name List of events
Fig List of Form events.

16. 12.3.1 Basic Event Handling Event name Event delegate
Event argument class
Fig Details of Click event.

17. 12.4 Control Properties and Layout
Common properties
Derive from class Control
Text property
Specifies the text that appears on a control
Focus method
Transfers the focus to a control
Becomes active control
TabIndex property
Order in which controls are given focus
Automatically set by Visual Studio .NET
Enable property
Indicate a control’s accessibility

18. 12.4 Control Properties and Layout
Visibility control
Hide control from user
Or use method Hide
Anchor property
Anchoring control to specific location
Constant distance from specified location
Unanchored control moves relative to the position
Docking allows control to spread itself along and entire side
Both options refer to the parent container
Size structure
Allow for specifying size range
MinimumSize and MaximumSize property

19. 12.4 Control Properties and Layout

20. 12.4 Control Properties and Layout
Before resize
After resize
Constant distance to left and top sides
Fig Anchoring demonstration.

21. 12.4 Control Properties and Layout
Darkened bar indicates to which wall control is anchored
Click down-arrow in Anchor property to display anchoring window
Fig Manipulating the Anchor property of a control.

22. 12.4 Control Properties and Layout
Control expands along top portion of the form
Fig Docking demonstration.

23. 12.4 Control Properties and Layout

24. 12.5 Labels, TextBoxes and Buttons
Provide text instruction
Read only text
Defined with class Label1
Derived from class Control
Textbox
Class TextBox
Area for text input
Password textbox

25. 12.5 Labels, TextBoxes and Buttons
Control to trigger a specific action
Checkboxes or radio buttons
Derived from ButtonBase

26. 12.5 Labels TextBoxes and Buttons

27. 12.5 Labels TextBoxes and Buttons

28. 12.5 Labels TextBoxes and Buttons

29. Visual Studio .NET adds comments to our code
1 // Fig : LabelTextBoxButtonTest.cs
2 // Using a Textbox, Label and Button to display
3 // the hidden text in a password box. 4
5 using System;
6 using System.Drawing;
7 using System.Collections;
8 using System.ComponentModel;
9 using System.Windows.Forms;
10 using System.Data; 11
12 // namespace contains our form to display hidden text
13 namespace LabelTextBoxButtonTest
14 {
/// <summary>
/// form that creates a password textbox and
/// a label to display textbox contents
/// </summary>
public class LabelTextBoxButtonTest :
System.Windows.Forms.Form {
private System.Windows.Forms.Button displayPasswordButton;
private System.Windows.Forms.Label displayPasswordLabel;
private System.Windows.Forms.TextBox inputPasswordTextBox; 25
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null; 30
// default contructor
public LabelTextBoxButtonTest() {
InitializeComponent(); }
LabelTextBoxButtonTest.cs
Visual Studio .NET adds comments to our code
The IDE manages these declaration
Visual Studio .NET inserts declarations for the control we added to the form
Declare reference components (an array)
Reference is null
Method InitializeComponent creates components and controls in the form and sets their properties
Constructor for the form is created for us

30. Method Dispose cleans up allocated resources36
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing ) {
if ( disposing ) {
if ( components != null ) {
components.Dispose(); } } 49
base.Dispose( disposing ); } 52
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent() {
this.displayPasswordButton =
new System.Windows.Forms.Button();
this.inputPasswordTextBox =
new System.Windows.Forms.TextBox();
this.displayPasswordLabel =
new System.Windows.Forms.Label();
this.SuspendLayout(); 67
LabelTextBoxButtonTest.cs
Method Dispose cleans up allocated resources
#region preprocessor directives allow collapsible code in Visual Studio .NET
Create new objects for the control we added

31. Visual Studio .NET register the event handler for us//
// displayPasswordButton //
this.displayPasswordButton.Location =
new System.Drawing.Point( 96, 96 );
this.displayPasswordButton.Name =
"displayPasswordButton";
this.displayPasswordButton.TabIndex = 1;
this.displayPasswordButton.Text = "Show Me";
this.displayPasswordButton.Click +=
new System.EventHandler(
this.displayPasswordButton_Click ); 80 //
// inputPasswordTextBox //
this.inputPasswordTextBox.Location =
new System.Drawing.Point( 16, 16 );
this.inputPasswordTextBox.Name =
"inputPasswordTextBox";
this.inputPasswordTextBox.PasswordChar = '*';
this.inputPasswordTextBox.Size =
new System.Drawing.Size( 264, 20 );
this.inputPasswordTextBox.TabIndex = 0;
this.inputPasswordTextBox.Text = ""; 93 //
// displayPasswordLabel //
this.displayPasswordLabel.BorderStyle =
System.Windows.Forms.BorderStyle.Fixed3D;
this.displayPasswordLabel.Location =
new System.Drawing.Point( 16, 48 );
this.displayPasswordLabel.Name =
"displayPasswordLabel";
LabelTextBoxButtonTest.cs
Visual Studio .NET register the event handler for us
Set the Name, PasswordChar and Text properties for inputPasswordTextBox

32. #endregion signal the end of the collapsible region
this.displayPasswordLabel.Size =
new System.Drawing.Size( 264, 23 );
this.displayPasswordLabel.TabIndex = 2;
106 //
// LabelTextBoxButtonTest //
this.AutoScaleBaseSize =
new System.Drawing.Size( 5, 13 );
this.ClientSize =
new System.Drawing.Size( 292, 133 );
this.Controls.AddRange(
new System.Windows.Forms.Control[] {
this.displayPasswordLabel,
this.inputPasswordTextBox,
this.displayPasswordButton});
this.Name = "LabelTextBoxButtonTest";
this.Text = "LabelTextBoxButtonTest";
this.ResumeLayout( false );
122
} // end method InitializeComponent
124
// end collapsible region started on line 53
#endregion
127
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main() {
Application.Run( new LabelTextBoxButtonTest() ); }
136
LabelTextBoxButtonTest.cs
#endregion signal the end of the collapsible region

33. LabelTextBoxButtonTest.cs Program Output
// display user input on label
protected void displayPasswordButton_Click(
object sender, System.EventArgs e ) {
// text has not changed
displayPasswordLabel.Text =
inputPasswordTextBox.Text; }
145
} // end class LabelTextBoxButtonTest
147
148 } // end namespace LabelTextBoxButtonTest
To show the text, set displayPasswordLabel’s Text to inputPasswordTextBox’s Text
Create an empty event handler named displayPasswordButton_Click
User must program this line manually
LabelTextBoxButtonTest.cs Program Output

34. Arrange components on a GUI
12.6 GroupBoxes and Panels
Arrange components on a GUI
GroupBoxes can display a caption
Text property determines its caption
Panels can have scrollbar
View additional controls inside the Panel

35. 12.6 GroupBoxes and Panels

36. 12.6 GroupBoxes and Panels

37. 12.6 GroupBoxes and Panels Controls inside panel panel
panel scrollbars
Fig Creating a Panel with scrollbars.

38. GroupBox (name mainGroupBox)
1 // Fig : GroupBoxPanelExample.cs
2 // Using GroupBoxes and Panels to hold buttons. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 /// form to display a groupbox versus a panel
12 public class GroupBoxPanelExample : System.Windows.Forms.Form
13 {
private System.Windows.Forms.Button hiButton;
private System.Windows.Forms.Button byeButton;
private System.Windows.Forms.Button leftButton;
private System.Windows.Forms.Button rightButton; 18
private System.Windows.Forms.GroupBox mainGroupBox;
private System.Windows.Forms.Label messageLabel;
private System.Windows.Forms.Panel mainPanel; 22
private System.ComponentModel.Container components = null; 24
// Visual Studio .NET-generated Dispose method 26
[STAThread]
static void Main() {
Application.Run( new GroupBoxPanelExample() ); } 32
GroupBoxPanelExample.cs
GroupBox (name mainGroupBox)
Panel (name mainPanel)
Control AutoScroll property set to TRUE
messageLabel is initially blank

39. hiButton and byeButton belong to GroupBox
// event handlers to change messageLabel 34
// event handler for hi button
private void hiButton_Click(
object sender, System.EventArgs e ) {
messageLabel.Text= "Hi pressed"; } 41
// event handler for bye button
private void byeButton_Click(
object sender, System.EventArgs e ) {
messageLabel.Text = "Bye pressed"; } 48
// event handler for far left button
private void leftButton_Click(
object sender, System.EventArgs e ) {
messageLabel.Text = "Far left pressed"; } 55
// event handler for far right button
private void rightButton_Click(
object sender, System.EventArgs e ) {
messageLabel.Text = "Far right pressed"; } 62
63 } // end class GroupBoxPanelExample
GroupBoxPanelExample.cs
hiButton and byeButton belong to GroupBox
Represent event handlers
Line messageLabel added to customize the text
Panel has two buttons, leftButton and rightButton

40. GroupBoxPanelExample.cs Program Output
hiButton_Click
leftButton_Click
rightButton_Click

41. 12.7 Checkboxes and RadioButtons
State buttons
On/off or true/false state
Derived from class ButtonBase
CheckBox
No restriction on usage
RadioButton
Grouped together
Only one can be true
Mutually exclusive options

42. 12.7 CheckBoxes and RadioButtons

43. When program start, both Checkbox is unchecked
1 // Fig : CheckBoxTest.cs
2 // Using CheckBoxes to toggle italic and bold styles. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 /// form contains checkboxes to allow
12 /// the user to modify sample text
13 public class CheckBoxTest : System.Windows.Forms.Form
14 {
private System.Windows.Forms.CheckBox boldCheckBox;
private System.Windows.Forms.CheckBox italicCheckBox; 17
private System.Windows.Forms.Label outputLabel; 19
private System.ComponentModel.Container components = null; 21
// Visual Studio .NET-generated Dispose method 23
/// The main entry point for the application.
[STAThread]
static void Main() {
Application.Run( new CheckBoxTest() ); } 30
CheckBoxTest.cs
When program start, both Checkbox is unchecked
Text property set to Bold
The Label OutputLabel is labeled Watch the font style change
Text property set to Italic

44. Font constructor takes in the font name, size, and style
// make text bold if not bold,
// if already bold make not bold
private void boldCheckBox_CheckedChanged(
object sender, System.EventArgs e ) {
outputLabel.Font =
new Font( outputLabel.Font.Name,
outputLabel.Font.Size,
outputLabel.Font.Style ^ FontStyle.Bold ); } 41
// make text italic if not italic,
// if already italic make not italic
private void italicCheckBox_CheckedChanged(
object sender, System.EventArgs e ) {
outputLabel.Font =
new Font( outputLabel.Font.Name,
outputLabel.Font.Size,
outputLabel.Font.Style ^ FontStyle.Italic ); } 52
53 } // end class CheckBoxTest
CheckBoxTest.cs
Font constructor takes in the font name, size, and style
Font object’s Style property is set when object is created
Style can use bitwise operators
Style property itself is read-only
Style is a member of the FontStyle enumeration

45. CheckBoxTest.cs Program Output
Result when bold is selected
Result when both styles are selected

46. 12.7 CheckBoxes and RadioButtons

47. Label is used to prompt user
1 // Fig : RadioButtonsTest.cs
2 // Using RadioButtons to set message window options. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 /// form contains several radio buttons--user chooses one
12 /// from each group to create a custom MessageBox
13 public class RadioButtonsTest : System.Windows.Forms.Form
14 {
private System.Windows.Forms.Label promptLabel;
private System.Windows.Forms.Label displayLabel;
private System.Windows.Forms.Button displayButton; 18
private System.Windows.Forms.RadioButton questionButton;
private System.Windows.Forms.RadioButton informationButton;
private System.Windows.Forms.RadioButton exclamationButton;
private System.Windows.Forms.RadioButton errorButton;
private System.Windows.Forms.RadioButton retryCancelButton;
private System.Windows.Forms.RadioButton yesNoButton;
private System.Windows.Forms.RadioButton yesNoCancelButton;
private System.Windows.Forms.RadioButton okCancelButton;
private System.Windows.Forms.RadioButton okButton;
private System.Windows.Forms.RadioButton
abortRetryIgnoreButton; 30
private System.Windows.Forms.GroupBox groupBox2;
private System.Windows.Forms.GroupBox groupBox1; 33
private MessageBoxIcon iconType = MessageBoxIcon.Error;
RadioButtonsTest.cs
Label is used to prompt user
Label is used to display which button was pressed
Display the text Display
RadioButtons are created for the enumeration options
One event handling exists for all the radio buttons in groupBox1 and groupBox2
To store user’s choice of options iconType is created.
The enumeration name indicate which button to display
Object iconType is a MessageBoxIcon enumeration

48. The enumeration name indicate which button to display
private MessageBoxButtons buttonType =
MessageBoxButtons.OK; 37
/// The main entry point for the application.
[STAThread]
static void Main() {
Application.Run( new RadioButtonsTest() ); } 44
// change button based on option chosen by sender
private void buttonType_CheckedChanged(
object sender, System.EventArgs e ) {
if ( sender == okButton ) // display OK button
buttonType = MessageBoxButtons.OK; 51
// display OK and Cancel buttons
else if ( sender == okCancelButton )
buttonType = MessageBoxButtons.OKCancel; 55
// display Abort, Retry and Ignore buttons
else if ( sender == abortRetryIgnoreButton )
buttonType = MessageBoxButtons.AbortRetryIgnore; 59
// display Yes, No and Cancel buttons
else if ( sender == yesNoCancelButton )
buttonType = MessageBoxButtons.YesNoCancel; 63
// display Yes and No buttons
else if ( sender == yesNoButton )
buttonType = MessageBoxButtons.YesNo; 67
// only one option left--display
// Retry and Cancel buttons
The enumeration name indicate which button to display
To store user’s choice of options buttonType is created
Object buttonType is a MessageBoxButtom enumeration
RadioButtonsTest.cs
Handlers compare the sender object with every radio button to determine which button was selected
Each radio button generates a CheckedChanged when clicked

49. Result of message box is a DialogResult enumeration
else
buttonType = MessageBoxButtons.RetryCancel; 72
} // end method buttonType_CheckedChanged 74
// change icon based on option chosen by sender
private void iconType_CheckedChanged(
object sender, System.EventArgs e ) {
if ( sender == errorButton ) // display error icon
iconType = MessageBoxIcon.Error; 81
// display exclamation point
else if ( sender == exclamationButton )
iconType = MessageBoxIcon.Exclamation; 85
// display information icon
else if ( sender == informationButton )
iconType = MessageBoxIcon.Information; 89
else // only one option left--display question mark
iconType = MessageBoxIcon.Question; 92
} // end method iconType_CheckedChanged 94
// display MessageBox and button user pressed
protected void displayButton_Click(
object sender, System.EventArgs e ) {
DialogResult result =
MessageBox.Show( "This is Your Custom MessageBox.",
"Custom MessageBox", buttonType, iconType, 0, 0 );
102
// check for dialog result and display it in label
switch ( result )
Handlers compare the sender object with every radio button to determine which button was selected
RadioButtonsTest.cs
Result of message box is a DialogResult enumeration
Click handler for displayButton creates a MessageBox
Switch statement tests for the result and set displayLabel.Text appropriately

50. {
case DialogResult.OK:
displayLabel.Text = "OK was pressed.";
break;
109
case DialogResult.Cancel:
displayLabel.Text = "Cancel was pressed.";
break;
113
case DialogResult.Abort:
displayLabel.Text = "Abort was pressed.";
break;
117
case DialogResult.Retry:
displayLabel.Text = "Retry was pressed.";
break;
121
case DialogResult.Ignore:
displayLabel.Text = "Ignore was pressed.";
break;
125
case DialogResult.Yes:
displayLabel.Text = "Yes was pressed.";
break;
129
case DialogResult.No:
displayLabel.Text = "No was pressed.";
break;
133
} // end switch
135
} // end method displayButton_Click
137
138 } // end class RadioButtonsTest
The result input will help determine which text to display among the cases
RadioButtonsTest.cs

51. RadioButtonsTest.cs Program Output
Radio button style allow user to select one per column
Exclamation icon type
Error icon type
OKCancel button type
OK button type

52. RadioButtonsTest.cs Program Output
Information icon type
Question icon type
AbortRetryIgnore button type
YesNoCancel button type
YesNo button type
RetryCancel button type

53. 12.8 PictureBoxes Class PictureBox Displays an image
Image set by object of class Image.
The Image property sets the Image object to use
SizeMode property sets how the image is displayed

54. 12.8 PictureBoxes

55. PictureBox imagePicture use to display one of three bitmap images
1 // Fig : PictureBoxTest.cs
2 // Using a PictureBox to display images. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data;
10 using System.IO; 11
12 /// form to display different images when clicked
13 public class PictureBoxTest : System.Windows.Forms.Form
14 {
private System.Windows.Forms.PictureBox imagePictureBox;
private System.Windows.Forms.Label promptLabel; 17
private int imageNum = -1; 19
/// The main entry point for the application.
[STAThread]
static void Main() {
Application.Run( new PictureBoxTest() ); } 26
// change image whenever PictureBox clicked
private void imagePictureBox_Click(
object sender, System.EventArgs e ) {
imageNum = ( imageNum + 1 ) % 3; // imageNum from 0 to 2 32
PictureBoxTest.cs
PictureBox imagePicture use to display one of three bitmap images
Includes instructions Click On Picture Box to View Images
Store the image we want to display
To respond to the Click event
Modulus calculation insures that number is between 0 and 2

56. PictureBoxTest.cs Program Output
// create Image object from file, display on PictureBox
imagePictureBox.Image = Image.FromFile(
Directory.GetCurrentDirectory() + "\\images\\image" +
imageNum + ".bmp" ); } 38
39 } // end class PictureBoxTest
Method FromFile which takes a string and creates an Image object
Set the Image property of imagePictureBox to an Image
Method GetCurrentDirectory of Class Directory returns current directory of file as a string
PictureBoxTest.cs Program Output
Use imageNum to append the correct number

57. 12.9 Mouse Event Handling Class MouseEventArgs
Contain coordinates of the mouse pointer
The mouse pressed
Number of clicks
Number of notches the wheel turned
Passing mouse event
Mouse event-handling methods take an object and MouseEventArgs object as argument
The Click event uses delegate EventHandler and event arguments EventArgs

58. 12.9 Mouse Event Handling

59. Creates variable shouldPaint to determine whether to draw on the form
1 // Fig 12.30: Painter.cs
2 // Using the mouse to draw on a form. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 /// creates a form as a drawing surface
12 public class Painter : System.Windows.Forms.Form
13 {
bool shouldPaint = false; // whether to paint 15
/// The main entry point for the application.
[STAThread]
static void Main() {
Application.Run( new Painter() ); } 22
// should paint after mouse button has been pressed
private void Painter_MouseDown(
object sender, System.Windows.Forms.MouseEventArgs e ) {
shouldPaint = true; } 29
// stop painting when mouse button released
private void Painter_MouseUp(
object sender, System.Windows.Forms.MouseEventArgs e ) {
shouldPaint = false; }
Painter.cs
Creates variable shouldPaint to determine whether to draw on the form
The event handler for event MouseDown
shouldPaint is set to true when this event occurs
Mouse cursor will draw
The event handler of event MouseUp
shouldPaint set to false, mouse cursor will not draw

60. Painter.cs Program Output36
// draw circle whenever mouse button
// moves (and mouse is down)
protected void Painter_MouseMove(
object sender, System.Windows.Forms.MouseEventArgs e ) {
if ( shouldPaint ) {
Graphics graphics = CreateGraphics();
graphics.FillEllipse(
new SolidBrush( Color.BlueViolet ),
e.X, e.Y, 4, 4 ); } 49
} // end Painter_MouseMove 51
52 } // end class Painter
Painter.cs Program Output
Creates the graphic object for the form
Program will draw only if shouldPaint is true
Method FillEllipse draws a circle at every point the mouse cursor moves over and shouldPaint is true
Provides method for drawing various shapes
Create new SolidBrush object by passing the constructor a Color value
Structure Color contain numerous predefined color constants
SolidBrush object determines the color of the shape drawn
Coordinates of x and y and the pixels height and width are supplied to the parameter list

61. 12.10 Keyboard Event Handling
Key events
Control that inherits from System.Windows.Forms.Control
Delegate KeyPressEventHandler
Event argument KeyPressEventArgs
KeyPress
ASCII character pressed
No modifier keys
Delegate KeyEventHandler
Event argument KeyEventArgs
KeyUp or KeyDown
Special modifier keys
Key enumeration value

62. 12.10 Keyboard Event Handling

63. Forms contain two Labels
1 // Fig : KeyDemo.cs
2 // Displaying information about the key the user pressed. 3
4 using System;
5 using System.Drawing;
6 using System.Collections;
7 using System.ComponentModel;
8 using System.Windows.Forms;
9 using System.Data; 10
11 // form to display key press
12 // information--contains two labels
13 public class KeyDemo : System.Windows.Forms.Form
14 {
private System.Windows.Forms.Label charLabel;
private System.Windows.Forms.Label keyInfoLabel; 17
private System.ComponentModel.Container components = null; 19
/// The main entry point for the application.
[STAThread]
static void Main() {
Application.Run( new KeyDemo() ); } 26
// display the character pressed using key char
protected void KeyDemo_KeyPress(
object sender, System.Windows.Forms.KeyPressEventArgs e ) {
charLabel.Text = "Key pressed: " + e.KeyChar; } 33
KeyDemo.cs
Label for key pressed
Initially empty
Forms contain two Labels
Label for modifier information
KeyPress event handler
Accesses the KeyChar property of the KeyPressEventArgs object
If key pressed is not ASCII, charLabel remains empty
Key pressed as a char
Display the key pressed

64. Uses Alt, Shift, and Control properties KeyEventArgs object KeyDemo.cs
// display modifier keys, key code, key data and key value
private void KeyDemo_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e ) {
keyInfoLabel.Text =
"Alt: " + ( e.Alt ? "Yes" : "No") + '\n' +
"Shift: " + ( e.Shift ? "Yes" : "No" ) + '\n' +
"Ctrl: " + ( e.Control ? "Yes" : "No" ) + '\n' +
"KeyCode: " + e.KeyCode + '\n' +
"KeyData: " + e.KeyData + '\n' +
"KeyValue: " + e.KeyValue; } 46
// clear labels when key released
private void KeyDemo_KeyUp(
object sender, System.Windows.Forms.KeyEventArgs e ) {
keyInfoLabel.Text = "";
charLabel.Text = ""; }
Uses Alt, Shift, and Control properties
KeyEventArgs object
KeyDemo.cs
Displays the KeyCode, KeyData, and KeyValue properties
KeyCode returns the key pressed without modifier keys information
KeyCode returns a Keys enumeration converted into a string using ToString
This block test for special keys, return bool if matched
KeyData property returns a Keys enumeration with data about modifier keys
KeyValue returns the key code as an integer
Integer value is the Windows virtual key code
KeyUp event handler clears both labels

65. KeyDemo.cs Program Output
Keys enumeration can test for specific keys by comparing key pressed to KeyCode
KeyDown event still raised so keyInfoLabel displays information
KeyPress event was not engaged