chapter eight string manipulation programming with microsoft visual basic 2010 5 th edition

Chapter EightString Manipulation

Programming with Microsoft Visual Basic 2010

5th Edition

Programming with Microsoft Visual Basic 2010, 5th Edition

Previewing the Hangman Game Application

2

Simplified version of classic Hangman game

Student must guess letter for mystery wordIf letter appears in word, it is added to blank

dashesIf letter does not appear in word, segment is

added to hangman imageHangman image has nine lines and one

circleGame is over when student correctly guesses

all letters in word or has 10 incorrect guesses

Programming with Microsoft Visual Basic 2010, 5th Edition3

Figure 8-1 Hangman Game application’s interface

Figure 8-2 Result of guessing the word


Lesson A Objectives

4

After studying Lesson A, you should be able to:

Determine the number of characters in a string

Remove characters from a stringInsert characters in a stringAlign the characters in a stringSearch a stringAccess characters in a stringCompare strings using pattern-matching


Working with Strings

5

Applications often need to manipulate string data

Two scenarios involving string manipulation Determine first character of an inventory part

numberSearch an address to find street name


Determining the Number of Characters in a String

6

Length propertyStores number of characters contained in

stringSyntax: string.LengthReturns integer value


Figure 8-3 Syntax and examples of the Length property


Removing Characters from a String

8

Trim methodRemoves space characters from both ends of

stringRemove method

Removes specified number of characters located anywhere in a string

Computer makes temporary copy of string in memory, then performs specified removal on copyOriginal string is not changedModified copy is returned to program


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


The Product ID Application

10

Product ID application displays listing of product IDs entered by user

Each product ID must contain exactly five characters


Figure 8-5 btnAdd control’s Click event procedure


Inserting Characters in a String

12

Insert methodInserts 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 argumentInteger specifying starting location to insert value

Represents the position in a stringTo insert at beginning of string:

Use startIndex of 0


Figure 8-6 Syntax and examples of the Insert method


Aligning the Characters in a String

14

PadLeft methodInserts zero or more characters at the

beginning of stringResults in string of a specified lengthRight-aligns the characters within the string

PadRight methodInserts characters at the end of the stringResults in string of a specified lengthLeft-aligns the characters within the string


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


The Net Pay Application

16

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


Figure 8-8 btnFormat control’s Click event procedure


Searching a String

18

Contains methodUsed to search string to find specific

sequence of charactersReturns a Boolean value

True if foundFalse otherwise

Must specify characters you are searching for

Begins search with first character in string


Searching a String (cont’d.)

19

IndexOf methodDetermine 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 searchIf not specified, starts searching with first

character in string


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


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


The City and State Application

22

Allows user to enter string:Composed of city name, comma, space, and

state nameDisplays index of the comma in the string


Figure 8-11 btnLocate control’s Click event procedure


The City and State Application (cont’d.)

24

Figure 8-12 Interface showing the comma’s index


Accessing the Characters in a String

25

Substring methodUsed to access any number of characters in

stringReturns string with specified number of

charactersSpecify index of first character to access in

string and number of characters to retrieveIf number of characters is not specified,

method returns all characters from startIndex position to the end of string


Figure 8-13 Syntax and examples of the Substring method


The Rearrange Name Application

27

Rearrange Name applicationAllows user to enter first name, space, and

last nameDisplays name as last name, comma, space,

first name


Figure 8-14 btnRearrange control’s Click event procedure


The Rearrange Name Application (cont’d.)

29

Figure 8-15 Interface showing the rearranged name


Using Pattern-Matching to Compare Strings

30

Like operatorAllows use of pattern-matching characters to

determine whether one string is equal to another

Must specify string to be examined and pattern to be matchedPattern can contain pattern-matching

charactersReturns Boolean value

Returns True if match is made, False otherwise


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

Programming with Microsoft Visual Basic 2010, 5th Edition32Figure 8-16 Syntax and examples of the Like operator (continues)


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


Using Pattern-Matching to Compare Strings (cont’d.)

34

Figure 8-16 Syntax and examples of the Like operator (cont’d.)


Modifying the Product ID Application

35

Product ID applicationUser enters product ID values of exactly five

charactersModification will ensure that entered five

characters consist of three letters followed by two numbers


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


Lesson A Summary

37

Visual Basic includes various string manipulation techniquesProperties: Length propertyMethods: Trim, Remove, Insert, Contains,

IndexOf, Substring, PadLeft, PadRightOperators: Like operator

Figure 8-18 summarizes syntax and purpose of each


Lesson B Objectives

38

After studying Lesson B, you should be able to:

Include a MenuStrip control on a formAdd elements to a menuAssign access keys to menu elementsAssign shortcut keys to commonly used

menu itemsCode a menu item’s Click event procedure


Adding a Menu to a Form

39

MenuStrip controlUsed to include one or more menus on a

formMenu title

Appears on menu bar at top of formMenu items can include:

Commands, submenu items, or separator bars

Clicking command on menu executes itClicking submenu item opens additional

menu Separator bars provides visual grouping


Adding a Menu to a Form (cont’d.)

40

Figure 8-19 Location of menu elements



41

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 standardsUse book title capitalization for menu item

captionsEllipsis (…) after item caption indicates menu

item requires more informationFile menu should be first item on menu barCut, Copy, Paste should appear on Edit menu


Figure 8-20 MenuStrip control added to the form



43

Figure 8-22 Drop-down list



44

Figure 8-23 File menu opened during run time


Assigning Shortcut Keys to Menu Items

45

Shortcut keysAppear to right of menu itemAllow you to select item without opening

menuExample: Ctrl+X and Ctrl+V

Cut and paste commandsAssign shortcut keys to commonly used

menu itemsFollow Windows standard conventions

Shortcut keys can be used when menu is closed


Assigning Shortcut Keys to Menu Items (cont’d.)

46

Figure 8-24 Shortcut key specified in the ShortcutKeys box


Assigning Shortcut Keys to Menu Items (cont’d.)

47

Figure 8-25 Location of the shortcut key on the menu


Coding the Exit Menu Item

48

How to end Hangman Game applicationUser clicks Exit item on File menuExit item’s Click event procedure calls Me.Close()


Lesson B Summary

49

MenuStrip controlCreates 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


Lesson C Objectives

50

After studying Lesson C, you should be able to:

Include the Length property in a procedureInclude the Substring method in a

procedureInclude the Like operator in a procedureInclude the Remove method in a procedureInclude the Insert method in a procedureInclude the Contains method in a procedure


Completing the Hangman Game Application

51

Application requirementsAllow one student to enter five-letter wordAllow another student to guess word, letter

by letter Two events can end game

Second student guesses all letters in wordSecond student makes 10 incorrect guesses


Coding the mnuFileNew Object’s Click Event Procedure

52

mnuFileNew object’s Click event procedure is invoked when user clicks New Game option on File menu

Two ways to begin new Hangman gameClick File on menu bar, then click New GamePress Ctrl + N


Coding the mnuFileNew Object’s Click Event Procedure (cont’d.)

53

Figure 8-29 Additional comments and code entered in the procedure



54

Figure 8-30 Comment and selection structure’s true path


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


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



57

Figure 8-33 Final comment and selection structure entered in the procedure



58

Figure 8-35 Result of entering the first incorrect letter



59

Figure 8-36 Result of guessing the word



60

Figure 8-37 Result of making 10 incorrect guesses


Lesson C Summary

61

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

chapter eight string manipulation programming with microsoft visual basic 2010 5 th edition

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