1. Chapter 8: String Manipulation

2. Previewing the Frankenstein Game Application
Figure 8-1 Interface for the Frankenstein Game application
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3. Previewing the Frankenstein Game Application (cont.)
Figure 8-2 Interface after guessing the secret word
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4. Previewing the Frankenstein Game Application (cont.)
Figure 8-3 Interface after not guessing the secret word
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5. 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
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6. Determining the Number of Characters in a String
Applications often need to manipulate string data
There are two scenarios involving string manipulation:
Determine the first character of an inventory part number
Search an address to find a street name
Length property
Stores the number of characters contained in a string
Syntax: string.Length
Returns an integer value
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7. Determining the Number of Characters in a String (cont.)
Figure 8-4 Syntax and examples of the Length property
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8. Removing Characters from a String
Trim method
Removes space characters from both ends of a string
Remove method
Removes a specified number of characters located anywhere in a string
The computer makes a temporary copy of the string in memory, and then performs the specified removal on the copy
The original string is not changed
The modified copy is returned to the program
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9. Removing Characters from a String (cont.)
Figure 8-5 Syntax and examples of the Trim and Remove methods
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10. Removing Characters from a String (cont.)
The Product ID Application
Figure 8-7 Sample run of the Product ID application
Figure 8-6 btnAdd control’s Click event procedure
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11. Inserting Characters in a String
Insert method
Inserts characters anywhere in a string
The computer makes a temporary copy of a string and inserts specified characters into the copy
Returns a string with the appropriate characters inserted
startIndex argument
An integer specifying the starting location to insert the value
Represents the position in a string
To insert the value at the beginning of a string, use a startIndex of 0
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12. Inserting Characters in a String (cont.)
Figure 8-8 Syntax and examples of the Insert method
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13. Inserting Characters in a String (cont.)
Aligning the Characters in a String
PadLeft method
Inserts zero or more characters at the beginning of a string
Results in a 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
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14. Inserting Characters in a String (cont.)
Aligning the Characters in a String (cont.)
Figure 8-9 Syntax and examples of the PadLeft and PadRight methods
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15. Inserting Characters in a String (cont.)
The Net Pay Application
Allows the user to enter the amount of the employee’s net pay
Displays the net pay with a leading dollar sign, asterisks, and two decimal places
Uses the Insert and PadLeft methods
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16. Inserting Characters in a String (cont.)
The Net Pay Application (cont.)
Figure 8-11 Interface showing the formatted net pay
Figure 8-10 btnFormat_Click procedure
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17. Searching a String Contains method
Used to search a string to find a specific sequence of characters
Returns a Boolean value
True if found
False otherwise
You must specify the characters you are searching for
The search begins with the first character in the string
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18. Searching a String (cont.)
IndexOf method
Determines if a string contains a character sequence
Returns an integer specifying the start position of a found character sequence (substring)
If the substring is not found, the method returns -1
You must specify the sequence of characters to search for
You may specify the index of the character at which to begin the search
If not specified, the search begins with the first character in the string
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19. Searching a String (cont.)
Figure 8-12 Syntax and examples of the Contains and IndexOf methods (continues)
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20. Searching a String (cont.)
Figure 8-12 Syntax and examples of the Contains and IndexOf methods
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21. Searching a String (cont.)
The City and State Application
Allows the user to enter a string
Composed of a city name, a comma, a space, and a state name
Displays index of the comma in the string
Figure 8-14 Interface showing the comma’s index
Figure 8-13 btnLocate_Click procedure
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22. Accessing the Characters in a String
Substring method
Used to access any number of characters in a string
Returns a string with a specified number of characters
Specify the index of the first character to access in the string, and the number of characters to retrieve
If the number of characters is not specified, the method returns all characters from the startIndex position to the end of the string
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23. Accessing the Characters in a String (cont.)
Figure 8-15 Syntax and examples of the Substring method
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24. Accessing the Characters in a String (cont.)
The Rearrange Name Application
Allows the user to enter a first name, a space, and a last name
Displays the name as last name, comma, space, first name
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25. Accessing the Characters in a String (cont.)
The Rearrange Name Application (cont.)
Figure 8-17 Interface showing the rearranged name
Figure 8-16 btnRearrange_Click procedure
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26. Using Pattern-Matching to Compare Strings
Like operator
Allows the use of pattern-matching characters to determine whether one string is equal to another
You must specify the string to be examined and the pattern to be matched
The pattern can contain pattern-matching characters
Returns a Boolean value
True if a match is made
False otherwise
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27. Using Pattern-Matching to Compare Strings (cont.)
Figure 8-18 Syntax and examples of the Like operator (continues)
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28. Using Pattern-Matching to Compare Strings (cont.)
(continued)
Figure 8-18 Syntax and examples of the Like operator (continues)
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29. Using Pattern-Matching to Compare Strings (cont.)
(continued)
Figure 8-18 Syntax and examples of the Like operator
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30. Using Pattern-Matching to Compare Strings (cont.)
Modifying the Product ID Application
Figure 8-20 Product ID added to the list box
Figure 8-19 Modified Click event procedure for the btnAdd control
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31. Lesson A Summary Programming with Microsoft Visual Basic 2012
Figure 8-21 String manipulation techniques
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32. 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
Enable and disable a control
Assign shortcut keys to commonly used menu items
Code a menu item’s Click event procedure
Include the Like operator in a procedure
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33. Adding a Menu to a Form Menu strip control
Used to include one or more menus on a form
A menu title appears on the menu bar at the top of the form
Menu items can include:
Commands
Submenu items
Separator bars
Clicking a command on a menu executes it
Clicking a submenu item opens an additional menu
Separator bars provide visual grouping
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34. Adding a Menu to a Form (cont.)
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
An ellipsis (…) after an item caption indicates a menu item requires more information
The FILE menu should be the first item on the menu bar
Cut, Copy, and Paste should appear on the EDIT menu
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35. Adding a Menu to a Form (cont.)
Figure 8-22 Location of menu elements
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36. Adding a Menu to a Form (cont.)
Figure 8-23 Six picture boxes selected in the interface
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37. Adding a Menu to a Form (cont.)
Figure 8-24 Current status of the form
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38. Adding a Menu to a Form (cont.)
Figure 8-25 MenuStrip control added to the form
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39. Adding a Menu to a Form (cont.)
Figure 8-26 Menu title included on the form
Figure 8-27 Drop-down list
Figure 8-28 FILE menu opened during run time
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40. Adding a Menu to a Form (cont.)
Assigning Shortcut Keys to Menu Items
Shortcut keys
Appear to the right of a menu item
Allow the user to select an item without opening a 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 a menu is closed
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41. Adding a Menu to a Form (cont.)
Assigning Shortcut Keys to Menu Items (cont.)
Figure 8-30 Location of the shortcut keys on the menu
Figure 8-29 Shortcut keys specified in the ShortcutKeys box
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42. Adding a Menu to a Form (cont.)
Coding the Exit Menu Item
How to end the Frankenstein Game application:
The user clicks the Exit item on the FILE menu
The Exit item’s Click event procedure calls Me.Close()
Coding the txtLetter Control’s KeyPress Event
Figure 8-31 txtLetter_KeyPress procedure
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43. Lesson B Summary To add a MenuStrip control to a form:
Use the MenuStrip tool, which is located in the Menus & Toolbars section of the toolbox
To create a menu:
Replace the words “Type Here” with the menu element’s caption
Assign a meaningful name and a unique access key to each menu element, with the exception of separator bars
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44. Lesson B Summary (cont.)
To include a separator bar on a menu:
Place your mouse pointer on a Type Here box and then click the list arrow that appears inside the box
Click Separator on the list
To enable/disable a control during run time:
Set its Enabled property to True (enable) or False (disable) either in the Properties window or in code
To assign shortcut keys to a menu item:
Set the menu item’s ShortcutKeys property
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45. 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 Remove method in a procedure
Include the Insert method in a procedure
Include the Contains method in a procedure
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46. Completing the Frankenstein Game Application
Figure 8-32 TOE chart for the Frankenstein Game application
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47. Completing the Frankenstein Game Application (cont.)
Figure 8-33 Interface for the Frankenstein Game application from Lesson B
Figure 8-34 Declaration statements for the class-level variables
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48. Completing the Frankenstein Game Application (cont.)
Coding the FILE Menu’s New Game Option
The mnuFileNew object’s Click event procedure is invoked when the user clicks the New Game option on the FILE menu
Two ways to begin a new game:
Click FILE on the menu bar, and then click New Game
Press Ctrl+N
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49. Completing the Frankenstein Game Application (cont.)
Coding the FILE Menu’s New Game Option (cont.)
Figure 8-35 Pseudocode for the mnuFileNew_Click procedure
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50. Completing the Frankenstein Game Application (cont.)
Coding the FILE Menu’s New Game Option (cont.)
Figure 8-36 Two ways of determining whether the word contains five letters
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51. Completing the Frankenstein Game Application (cont.)
Coding the FILE Menu’s New Game Option (cont.)
Figure 8-37 Results of entering a valid word
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52. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure
Figure 8-38 Pseudocode for the btnCheck_Click, DisplayPicture, and DetermineGameOver procedures (continues)
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53. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
(continued)
Figure 8-38 Pseudocode for the btnCheck_Click, DisplayPicture, and DetermineGameOver procedures
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54. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
Figure 8-39 Additional code entered in the btnCheck_Click procedure
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55. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
Figure 8-40 Result of guessing the secret word
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56. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
Figure 8-41 Result of not guessing the secret word
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57. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
Figure 8-42 Frankenstein Game application’s code (continues)
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58. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
(continued)
Figure 8-42 Frankenstein Game application’s code (continues)
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59. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
(continued)
Figure 8-42 Frankenstein Game application’s code (continues)
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60. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
(continued)
Figure 8-42 Frankenstein Game application’s code (continues)
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61. Completing the Frankenstein Game Application (cont.)
Completing the Check Button’s Click Event Procedure (cont.)
(continued)
Figure 8-42 Frankenstein Game application’s code
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62. Lesson C Summary Length property: Determines the length of a string
Substring method: Accesses one or more characters in a string
Like operator: Uses pattern-matching to compare two strings
Remove method: Removes a specified number of characters located anywhere in a string
Insert method: Inserts characters anywhere in a string
Contains method: Determines whether a specific character is contained in a string
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