1. Programming with Microsoft Visual Basic 2010 5th Edition
Chapter Eight
String Manipulation

2. Previewing the Hangman Game Application
Simplified version of classic Hangman game
Student must guess letter for mystery word
If letter appears in word, it is added to blank dashes
If letter does not appear in word, segment is added to hangman image
Hangman image has nine lines and one circle
Game is over when student correctly guesses all letters in word or has 10 incorrect guesses

3. Figure 8-1 Hangman Game application’s interface
Figure 8-2 Result of guessing the word

4. Lesson A Objectives After studying Lesson A, you should be able to:
Determine the number of characters in a string
Remove characters from a string
Insert characters in a string
Align the characters in a string
Search a string
Access characters in a string
Compare strings using pattern-matching

5. Working with Strings Applications often need to manipulate string data
Two scenarios involving string manipulation
Determine first character of an inventory part number
Search an address to find street name

6. Determining the Number of Characters in a String
Length property
Stores number of characters contained in string
Syntax: string.Length
Returns integer value

7. Figure 8-3 Syntax and examples of the Length property

8. Removing Characters from a String
Trim method
Removes space characters from both ends of string
Remove method
Removes specified number of characters located anywhere in a string
Computer makes temporary copy of string in memory, then performs specified removal on copy
Original string is not changed
Modified copy is returned to program

9. Figure 8-4 Syntax and examples of the Trim and Remove methods

10. The Product ID Application
Product ID application displays listing of product IDs entered by user
Each product ID must contain exactly five characters

11. Figure 8-5 btnAdd control’s Click event procedure

12. Inserting Characters in a String
Insert method
Inserts characters anywhere in a string
Computer makes temporary copy of string and inserts specified characters into the copy
Returns string with appropriate characters inserted
startIndex argument
Integer specifying starting location to insert value
Represents the position in a string
To insert at beginning of string:
Use startIndex of 0

13. Figure 8-6 Syntax and examples of the Insert method

14. Aligning the Characters in a String
PadLeft method
Inserts zero or more characters at the beginning of string
Results in string of a specified length
Right-aligns the characters within the string
PadRight method
Inserts characters at the end of the string
Left-aligns the characters within the string

15. Figure 8-7 Syntax and examples of the PadLeft and PadRight methods

16. The Net Pay Application
Allows user to enter amount of employee’s net pay
Displays net pay with leading dollar sign, asterisks, and two decimal places
Uses the Insert and PadLeft methods

17. Figure 8-8 btnFormat control’s Click event procedure

18. Searching a String Contains method
Used to search string to find specific sequence of characters
Returns a Boolean value
True if found
False otherwise
Must specify characters you are searching for
Begins search with first character in string

19. Searching a String (cont’d.)
IndexOf method
Determine if string contains character sequence
Returns integer specifying start position of found character sequence (substring)
If substring is not found, method returns -1
Must specify sequence of characters to search for
May specify index of character at which to begin search
If not specified, starts searching with first character in string

20. Figure 8-10 Syntax and examples of the Contains and IndexOf methods (continues)

21. Figure 8-10 Syntax and examples of the Contains and IndexOf methods (cont’d.)

22. The City and State Application
Allows user to enter string:
Composed of city name, comma, space, and state name
Displays index of the comma in the string

23. Figure 8-11 btnLocate control’s Click event procedure

24. The City and State Application (cont’d.)
Figure 8-12 Interface showing the comma’s index

25. Accessing the Characters in a String
Substring method
Used to access any number of characters in string
Returns string with specified number of characters
Specify index of first character to access in string and number of characters to retrieve
If number of characters is not specified, method returns all characters from startIndex position to the end of string

26. Figure 8-13 Syntax and examples of the Substring method

27. The Rearrange Name Application
Allows user to enter first name, space, and last name
Displays name as last name, comma, space, first name

28. Figure 8-14 btnRearrange control’s Click event procedure

29. The Rearrange Name Application (cont’d.)
Figure 8-15 Interface showing the rearranged name

30. Using Pattern-Matching to Compare Strings
Like operator
Allows use of pattern-matching characters to determine whether one string is equal to another
Must specify string to be examined and pattern to be matched
Pattern can contain pattern-matching characters
Returns Boolean value
Returns True if match is made, False otherwise

31. Figure 8-16 Syntax and examples of the Like operator (continues)

32. Figure 8-16 Syntax and examples of the Like operator (continues)

33. Figure 8-16 Syntax and examples of the Like operator (continues)

34. Using Pattern-Matching to Compare Strings (cont’d.)
Figure 8-16 Syntax and examples of the Like operator (cont’d.)

35. Modifying the Product ID Application
User enters product ID values of exactly five characters
Modification will ensure that entered five characters consist of three letters followed by two numbers

36. Figure 8-17 Modified Click event procedure for the btnAdd control

37. Lesson A Summary
Visual Basic includes various string manipulation techniques
Properties: Length property
Methods: Trim, Remove, Insert, Contains, IndexOf, Substring, PadLeft, PadRight
Operators: Like operator
Figure 8-18 summarizes syntax and purpose of each

38. Lesson B Objectives After studying Lesson B, you should be able to:
Include a MenuStrip control on a form
Add elements to a menu
Assign access keys to menu elements
Assign shortcut keys to commonly used menu items
Code a menu item’s Click event procedure

39. Adding a Menu to a Form MenuStrip control Menu title
Used to include one or more menus on a form
Menu title
Appears on menu bar at top of form
Menu items can include:
Commands, submenu items, or separator bars
Clicking command on menu executes it
Clicking submenu item opens additional menu
Separator bars provides visual grouping

40. Adding a Menu to a Form (cont’d.)
Figure 8-19 Location of menu elements

41. Adding a Menu to a Form (cont’d.)
Menu title captions should be one word only
Menu item captions can be from one to three words
Assign unique access keys to menu titles and items
Follow Windows menu standards
Use book title capitalization for menu item captions
Ellipsis (…) after item caption indicates menu item requires more information
File menu should be first item on menu bar
Cut, Copy, Paste should appear on Edit menu

42. Figure 8-20 MenuStrip control added to the form

43. Adding a Menu to a Form (cont’d.)
Figure 8-22 Drop-down list

44. Adding a Menu to a Form (cont’d.)
Figure 8-23 File menu opened during run time

45. Assigning Shortcut Keys to Menu Items
Appear to right of menu item
Allow you to select item without opening menu
Example: Ctrl+X and Ctrl+V
Cut and paste commands
Assign shortcut keys to commonly used menu items
Follow Windows standard conventions
Shortcut keys can be used when menu is closed

46. Assigning Shortcut Keys to Menu Items (cont’d.)
Figure 8-24 Shortcut key specified in the ShortcutKeys box

47. Assigning Shortcut Keys to Menu Items (cont’d.)
Figure 8-25 Location of the shortcut key on the menu

48. Coding the Exit Menu Item
How to end Hangman Game application
User clicks Exit item on File menu
Exit item’s Click event procedure calls Me.Close()

49. Lesson B Summary MenuStrip control
Creates menu on form
Menu items can include commands, submenu items, and separator bars
Assign unique access key to each menu element:
Except separator bars
Assign shortcut keys to commonly used menu items
Follow Windows standard when creating menus

50. Lesson C Objectives After studying Lesson C, you should be able to:
Include the Length property in a procedure
Include the Substring method in a procedure
Include the Like operator in a procedure
Include the Remove method in a procedure
Include the Insert method in a procedure
Include the Contains method in a procedure

51. Completing the Hangman Game Application
Application requirements
Allow one student to enter five-letter word
Allow another student to guess word, letter by letter
Two events can end game
Second student guesses all letters in word
Second student makes 10 incorrect guesses

52. Coding the mnuFileNew Object’s Click Event Procedure
mnuFileNew object’s Click event procedure is invoked when user clicks New Game option on File menu
Two ways to begin new Hangman game
Click File on menu bar, then click New Game
Press Ctrl + N

53. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-29 Additional comments and code entered in the procedure

54. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-30 Comment and selection structure’s true path

55. Figure 8-31 Additional comments and selection structure entered in the procedure

56. Figure 8-32 Additional comments and selection structures entered in the procedure

57. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-33 Final comment and selection structure entered in the procedure

58. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-35 Result of entering the first incorrect letter

59. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-36 Result of guessing the word

60. Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)
Figure 8-37 Result of making 10 incorrect guesses

61. Lesson C Summary
Use string’s Length property to determine length of string
Use Substring method to access one or more characters in a string
Use the Like operator to compare two strings
Use the Remove method to remove specified characters anywhere in a string
Use Insert method to insert characters in a string
Use Contains method to determine whether a specific character is contained in a string