1. Repetition and Multiple Forms
Chapter 6
Repetition and Multiple Forms

2. Objectives Add a second form to a solution
Define a solution's startup object
Create an object programmatically
Write Do and For loops to execute statements repeatedly
Draw and paint shapes on a form
Use the Timer control
Display, close, and hide forms
Design a report
Use the PrintPreviewDialog and PrintDocument controls to print a report preview to the screen
Use the StringFormat class

3. Adding a Form to a Solution (1)
Most applications are made up of multiple forms
To add a new form, click Project and then click Add New Item
Select the type of item to add from the dialog box
To add an existing form, click Project, and then click Add Existing Item

4. Adding a Form to a Solution (2)
Local Project Items folder expanded
Select Windows Form
Enter form name

5. Defining the Startup Object (1)
Every solution has one startup object
Startup object can be a form or a sub procedure named Main
Set the startup object using the Project's General Property Page
Right-click the project in the Solution Explorer, and then select Property Pages to activate the Property Pages

6. Defining the Startup Object (2)
General tab selected
Startup object is Sub Main

7. Creating an Object Programmatically
The Win Form Designer writes statements to create control instances
This code is typically collapsed and appears in the region "Windows Form Designer generated code"
You can write statements to create form and control instances too
To create an object, declare a variable with the New keyword
Data type is the class name
For a form, this is the value of the Name property
Create an instance of the form named frmSplash
Dim frmNew As New frmSplash()

8. Displaying a Form as a Modal Dialog Box
Call ShowDialog method of the form
When a form is displayed as a modal dialog, form must be close before other forms can get focus
Note that form's constructor is called when form instance is created
Display the form using the variable frmNewSplash
Dim frmNewSplash As New frmSplash frmNewSplash.ShowDialog()

9. Executing Statements Repeatedly (1)
A Do Loop executes statements repeatedly until some condition becomes True or False
Note that the same Do loop can be written in different ways
Do loop has the following syntax:
Do [ While | Until ] condition
[ Statements ]
[ Exit Do ]
Loop

10. Executing Statements Repeatedly (2)
Do While and Do Until loops evaluate a condition before executing the statements in the loop
Condition evaluates to a Boolean value
Syntax is the same as the condition in an If statement
While keyword causes statements to execute while a condition is true
Until keyword causes statements to execute until a condition becomes true
Exit Do statement marks the end of the Do Loop

11. Do While Loop (Example)
Print the numbers from 1 to 10 to the Output window
Dim pintCounter As Integer
Do While pintCounter <= 10
Debug.WriteLine(pintCounter)
pintCounter = pintCounter + 1
Loop

12. Do While Loop (Analysis)
Dim pintCounter As Integer = 1
Initialize loop variable
Test condition again
Do Until pintCounter > 10
Test condition
(pintCounter > 10)
True
Debug.WriteLine(pintCounter)
pintCounter = pintCounter + 1
Loop
False
 statements
Exit loop

13. Do Until Loop (Example)
Print the numbers from 1 to 10 to the Output window Dim pintCounter As Integer
Do Until pintCounter > 10
Debug.WriteLine(pintCounter)
pintCounter = pintCounter + 1
Loop

14. Do Until Loop (Analysis)
Dim pintCounter As Integer = 1
Initialize loop variable
Test condition again
Do While pintCounter <= 10
Test condition
(pintCounter <= 10)
True
Debug.WriteLine(pintCounter)
pintCounter = pintCounter + 1
Loop
False
 statements
Exit loop

15. Do Loop While and Do Loop Until
Do Loop While and Do Loop Until statements test condition after executing the statements in the loop instead of before
Loop statements will always execute at least once Do
[ Statements ]
[ Exit Do ]
Loop [ While | Until ] condition

16. Do Loop While and Do Loop Until (Example)
Print the numbers 1 to 10 to the Output window
Dim pintCounter As Integer = 1 Do
Debug.WriteLine(pintCounter)
pintCount = pintCounter + 1
Loop While Counter <= 10

17. Do Loop While (Analysis)
Initialize loop variable
Dim pintCounter As Integer = 1 Do
Debug.WriteLine(pintCounter)
pintCounter = pintCounter + 1
Execute statements
Execute statements again
Test condition
(pintCounter <= 10)
True
Loop While pintCounter <= 10
False
 statements
Exit loop

18. Counters and Accumulators
A counter is a variable, used in a loop, whose value is increased by 1 each time through the loop
A counter has the following general form
Counter = Counter + 1
An accumulator is a variable, used in a loop whose value is incremented so as to calculate a total
An accumulator has the following general form
Accumulator = Accumulator + 1

19. Shorthand Notation for Counters and Accumulators
+=, -=, *=, /= are shorthand operators
The following statements are equivalent
Note that both illustrate the use of a counter
pintCounter = pintCounter + 1
pintCounter +=1

20. Infinite Loops Loops that never exit are called infinite loops
Infinite loops happen when a condition does not ever occur that causes the loop to exit
Click the Break button on the Debug toolbar to suspend execution
The following loop prints the value 1 to the Output window forever:
Dim pintCounter = 1
Do Until pintCounter > 10
Debug.WriteLine pintCounter
Loop

21. The For Loop Similar to a Do loop
Executes statements repeatedly using a counter
Use when you know in advance how many times the loop will execute
Executes faster than a comparable Do Loop
Any For loop can be written as a Do Loop but not the other way around

22. For Loop Syntax (1)
For loop executes statements between For and Next a fixed number of times
For counter = start To end [ Step increment ]
[ Statements ]
Exit For
Next [ counter ]

23. For Loop Syntax (2)
counter is set to start when the loop is initialized
Statements in loop execute until counter becomes greater than end
Note VB .NET automatically sets the value of counter
counter is incremented by 1 by default
Use Step increment clause to increment or decrement counter by a different value
The Exit For statement causes the For loop to exit immediately
Note that the value of counter is preserved

24. For Loop (Analysis) VB.NET initializes pintCounter to 1 (start)
For pintCounter = 1 To 10
VB.NET increments pintCounter and tests condition again. Increment is not specified so increment by 1
Test condition
(pintCounter <= 10)
True
Debug.WriteLine pintCounter
Next pintCounter
statements
Exit loop when start is greater than end
False

25. For Loop (Example 1)
Print the numbers 1 through 10 to the Output window
Dim pintCounter As Integer
For pintCounter = 1 To 10
Debug.WriteLine pintCounter
Next pintCounter

26. For Loop (Example 2)
Print the values from 2000 to 1900 to the Output window decrementing the value by 5 each time
Dim pintYear As Integer
For pintYear = 2000 To 1900 Step -5
Debug.Writeline(pintYear)
Next pintYear

27. Introduction to Drawing
Graphical Device Interface (GDI) provides standardized classes and methods to draw shapes to a graphical output device
Output device can be a form
Output device can be a printer
System.Drawing namespace contains classes to define shapes
Graphics class provides methods to draw to an output device

28. The System.Drawing Namespace
Use to define graphical elements
Rectangle structure defines the size and position of a rectangle
SolidBrush class defines a brush made up of a single color
Pen class is used to draw lines and outline a rectangle
Font class defines typeface, size, and other attributes for text

29. Graphics Class
Methods draw shapes and text to a graphical output device
DrawLine method draws a line between two points using a Pen
DrawRectangle method draws an outline of a rectangle using a Pen
FillRectangle method draws a filled rectangle using a brush
DrawString method draws a string of characters using a font, a color, and a brush

30. Steps to Create and Draw a Rectangle
Create an instance of the Rectangle
Use Size and Point structures or define the x and y coordinates
Create an instance of the Pen class to define the color and width of the border surrounding the rectangle
Call the DrawRectangle method of the Graphics class to draw the rectangle outline

31. The Point Structure
The Point structure defines starting point or ending point of a line, or the upper-left corner of a rectangle
Standard prefix is "pnt"
Syntax:
Overloads Public Sub New ( x As Integer, y As Integer )
x and y arguments define the point's coordinates
Upper-left corner of device is 0, 0

32. The Point Structure (Example)
The following statement creates a new point at the upper-left corner of the output device:
Dim pntCurrent As New Point(0, 0)

33. The Size Structure Defines the size of a Rectangle
Standard prefix is "siz"
Syntax:
Overloads Public Sub New( width As Integer, height As Integer )
width and height arguments define horizontal and vertical distance
Values are measured in points

34. The Size Structure (Example)
Create a size 1 inch square
Dim sizCurrent As New Size(72, 72)

35. Rectangle Constructor
Overloaded constructor creates a rectangle
Standard prefix for a rectangle is "rec"
One syntax variation uses existing Point and Size structures. The other uses the x, y coordinates, width and height
Syntax:
Overloads Public Sub New( location As Point, size As Size )
Overloads Public Sub New( x As Integer, y As Integer, width As Integer, height As Integer )

36. Rectangle Constructor (Example)
Create a new Rectangle with existing Point and Size structures
Dim pntCurrent As New Point(0, 0)
Dim sizCurrent As New Size(72, 72)
Dim recCurrent As New _
Rectangle(pntCurrent, sizCurrent)
Create a new Rectangle without Point and Size structures Dim recCurrent As Rectangle
recCurrent = New Rectangle(0, 0, 72, 72)

37. Understanding Color
Computer monitors display colors by combining varying intensities of red, green, and blue colors
The term RGB (red, green blue) describes these colors
The alpha value defines the brightness of a color
RGB values range from 0 to 255
0 means that color is turned of
255 means that color is applied at its full intensity

38. Color Structure Belongs to the System.Drawing namespace
Several named colors are supported
Blue, Red, Yellow, etc…
Create new colors using the FromArgb method
R, G, B properties contain an RGB value
"col" is the standard prefix for color
Examples
Dim colCurrent As Color = Color.Blue
Dim colCurrent As Color = Color.Red

39. Creating a Color Overloaded FromArgb method creates a new color
FromArgb is a static method so do not use New keyword
Overloads Public Shared Function FromArgb( red As Integer, green As Integer, blue As Integer )
red, green, and blue arguments contain RGB values

40. FromArgb Method (Example)
Create a new color (white)
Dim colCurrent As Color
colCurrent = Color.FromArgb(255, 255, 255, 255)

41. Brushes Used to fill rectangles
Standard prefix for a SolidBrush is "sb"
SolidBrush constructor creates a brush having a solid color
Syntax:
Public Sub New( color As Color )
color argument contains an existing color
Use named color or a color created from FromArgb method

42. Brushes (Example) Create a solid brush using a new color
Dim colCurrent As Color = _
Color.FromArgb(255,255,255)
Dim sbCurrent = New SolidBrush(colCurrent)
Create a solid brush using a named color
Dim sbCurrent = New SolidBrush(Color.Red)

43. Filling a Rectangle
Fill a rectangle by calling the overloaded FillRectangle method
Two syntax variations
The first uses an existing Rectangle structure
In the second, you define the size and shape of the rectangle
Syntax:
Overloads Public Sub FillRectangle( brush As Brush, rect As Rectangle )
Overloads Public Sub FillRectangle( brush As Brush, x As Single, y As Single, width As Single, height As Single )

44. FillRectangle Method (Example)
Assume that the variable "e" references an instance of the Graphics class
Code would appear in the form's Paint event handler
Dim colCurrent As Color = _ Color.FromArgb(255, 255, 255)
Dim sbCurrent = New SolidBrush(colCurrent)
e.Graphics.FillRectangle(sbCurrent, 0, 0, 72, 72)

45. Introduction to Pens Use pens to draw lines
Standard prefix for a pen is "pen"
Syntax:
Overloads Public Sub New( color As Color )
Overloads Public Sub New( color As Color, width As Single )
color is named color or created color
width is thickness of the line
Unit of measure is points

46. Creating a Pen (Example)
Create a blue pen 3 points in width
Dim penCurrent As New Pen(Color.Blue, 3)

47. Drawing an Outlined Rectangle
Call the DrawRectangle method of the Graphics class
First method uses an existing Rectangle structure and the second uses rectangle coordinates and size
Syntax:
Overloads Public Sub DrawRectangle( pen As Pen, rect As Rectangle )
Overloads Public Sub DrawRectangle( pen As Pen, x As Integer, y As Integer, width As Integer, height As Integer )

48. DrawRectangle Method (Example)
Create an outlined rectangle the size of the form
Assume that graCurrent references an instance of the Graphics class
Dim penCurrent As New Pen(Color.Blue, 3)
Dim recCurrent As Rectangle
recCurrent = New Rectangle(0, 0, _
Me.Width – 3, Me.Height – 3)
graCurrent.DrawRectangle(penCurrent, recCurrent)

49. DrawLine Method Draws a line using a Pen
Use existing Point structures or specify x,y coordinate values
Syntax:
Overloads Public Sub DrawLine( pen As Pen, point As Point, point As Point )
Overloads Public Sub DrawLine( pen As Pen, x1 As Integer, y1 As Integer, x2 As Integer, y2 As Integer )

50. DrawLine Method (Example)
Draw a line using x,y coordinate values
Assume that e references an instance of the Graphics class
Dim penLine As New Pen(Color.Red, 3)
e.Graphics.DrawLine(penLine, 0, 0, _ , 100)

51. Drawing Text Create a font using the Font constructor
Font constructor creates a Font object using:
Font name or family
Font size
Font style
Draw a string using an existing Font and brush by calling the DrawString method

52. Font Class Standard prefix for the Font class is "fnt" Properties
Bold, Italic, Strikeout, and Underline properties define whether a particular font attribute is applied or not
Name property gets font name
SizeInPoints property gets the font size
Value is measured in points
Methods
GetHeight method gets font height using current graphics context

53. Font Constructor Syntax:
Overloads Public Sub New( family As String, emSize As Single )
Overloads Public Sub New( family As String, emSize As Single, style As FontStyle)
Family argument contains font name
emSize contains font size in points
Style defines attributes applied to the font (Bold, Italic, Underline, etc.)

54. Font Constructor (Example)
Create a 14 point, bold, Arial font
Dim fntSplash As New Font("Arial", _
14, FontStyle.Bold)

55. DrawString method
Draws text to a graphics device using an existing font
Syntax:
Overloads Public Sub DrawString( s As String, font As Font, brush As Brush, x As Single, y As Single )
Overloads Public Sub DrawString( s As String, font As Font, brush As Brush, x As Single, y As Single, format As StringFormat )

56. DrawString (Example)
Draw a string using the previously created font named fntSplash, and a green brush
Upper-left corner is 5, 265
Assume graCurrent references an instance of the Graphics class
graCurrent.DrawString( _
"Copyright 2003 – Course Technology", _
fntSplash, Brushes.Green, 5, 265)

57. The Timer Control
Fires a Tick event at regular intervals based on the setting of the Interval property
Control is not visible at run time so the control instance appears in resizable tray at the bottom of the form
Properties
Boolean Enabled property controls whether Tick event fires
Interval property controls number of milliseconds between Tick events
Events
Tick event fires each Interval

58. Displaying, Closing, and Hiding Forms
Call the Show method to display a form
Call the ShowDialog method to display a form as a modal dialog box
Call the Hide method to hide a form but leave the form in memory
Call the Close method to close the form and remove it from memory

59. Introduction to Report Design
Just as designing forms is important so too is report design
Reports should have a title that is centered on the page
Column headers and columns should be aligned
Decimal points should be aligned in column
Evenly space columns

60. Completed Report

61. The PrintPreviewDialog Control (1)
Create a report image on the desktop which can be sent to the printer
Standard prefix is "ppd"
Buttons allow zooming and navigation from one page to another
Use the same drawing methods that you used to draw graphics to a form

62. The PrintPreviewDialog Control (2)
Properties
Text property appears in the title bar
Document property defines the document to preview
Set property to instance of the PrintDocument control
Location property defines the upper-left corner of the visible region
MinimizeBox and MaximizeBox properties control the buttons that appear on the title bar
Top, Left, Height, and Width properties define the position and size of the control instance
Method
ShowDialog method displays the dialog box

63. The PrintDocument Control
Works in conjunction with the PrintPreviewDialog control
Standard prefix is "pd"
Provides the reference to the Graphics object
Similar to the way the Paint event supplies a reference to the Graphics class

64. The PrintDocument Control (Properties and Methods)
PrinterSettings property contains a reference to a PrinterSettings object
Object contains information about the printer
Events
BeginPrint event fires before first page is printed
EndPrint event fires after last page has printed
PrintPage event occurs for each page printed

65. Printing Coordinates (1)
Piece of paper has a fixed size (typically 8 ½ x 11 inches)
Upper-left corner has (x, y) coordinates of (0, 0)
Lower-right corner has (x, y) coordinates of (850, 1100)
Unit of measure is 1/100 of an inch

66. Printing Coordinates (2)
x-axis
0,0
850,0
y-axis
0,1100
850,1100

67. Handling Printing Events
PrintPage event applies to the PrintDocument class
Supplies a reference to the PrintPageEventArgs class
PrintPageEventArgs class, in turn supplies a reference to the Graphics object

68. PrintPageEventArgs class
Properties
HasMorePages defines whether additional pages need to be printed
Set property to false when finished printing
MarginBounds property defines the area inside the page margin
PageBounds defines the size of the paper
PageSettings defines general printer characteristics such as whether paper orientation

69. The StringFormat Class
Applies to the System.Drawing namespace
Alignment property controls how text is aligned in a rectangle
Trimming property defines how characters are truncated
If set to Character, text is trimmed to the nearest character
If set to Word, then the characters are trimmed to the nearest word