Programming with Microsoft Visual Basic 2008 Fourth Edition Chapter Eight String Manipulation.

Programming with Microsoft Visual Basic 2008

Fourth Edition

Chapter Eight

String Manipulation

Working with Strings

• Applications often need to manipulate string data

• Two scenarios involving string manipulation – Determine first letter of an inventory part id– Search an address to find street name

2Programming with Microsoft Visual Basic 2008, Fourth Edition

Determining the Number of Characters in a String

• Length property:– Stores number of characters contained in string

• Syntax: string.Length• Returns integer value


Removing Spaces from the Beginning and End of a String

• Trim method:– Removes spaces from both ends of string

• Computer makes temporary copy of string in memory, then performs trimming on copy– Original string is not changed– Modified copy is returned to program


Replacing Characters in a String

• Replace method:– Replaces one sequence of characters with another

• Example: Replace area code “800” with “877”

• Must specify both sequence of characters in string to be replaced, and replacement characters to be used

• Computer makes temporary copy of string and replaces specified characters in copy

• Returns string that includes replaced characters


Replacing Characters in a String (continued)

6Programming with Microsoft Visual Basic 2008, Fourth EditionFigure 8-6: Syntax, purpose, and examples of the Replace method

The Mid Statement

• Mid statement: – Replaces set of characters with another string

• Must specify:– targetString: String targeted for character

replacement– replacementString: Contains replacement

characters to be used– start: Position of first character of targetString

where replacement should take place– count: Number of characters to replace in

targetString


The Mid Statement (continued)


Figure 8-7: Syntax, purpose, and examples of the Mid statement

Inserting Characters in a String

• PadLeft method:– Inserts padded characters at start of string – Right-aligns characters within string

• PadRight method:– Inserts padded characters at end of string– Left-aligns characters within string

• Must specify character to pad with, and desired final total length of target string– If no character is specified, space is used


Insert Method

• Insert method:– Inserts characters anywhere within string

• Examples: – Insert middle initial within employee name– Insert parentheses around area code in phone

number

• Must specify position (index) where new characters will be inserted


Insert Method (continued)


Figure 8-11: Syntax, purpose, and example of the Insert method

Accessing Characters Contained in a String

• Substring method: – Used to access any number of characters in string– Returns string with specified number of characters

• Must specify index of first character to access in string, and number of characters to retrieve– If number of characters is not specified, all

characters from start position to the end of string are returned


Accessing Characters Contained in a String (continued)


Figure 8-18: Syntax, purpose, and examples of the Substring methodc

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


Using Pattern-Matching to Compare Strings (continued)


Figure 8-21: Syntax, purpose, and examples of the Like operator

Adding a Menu to a Form

• MenuStrip control: Used to include one or more menus in application

• 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


Adding a Menu to a Form (continued)


Figure 8-24: Location of menu elements

Adding a Menu to a Form (continued)

• 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:– Ellipsis (…) after item caption indicates dialog box

will display for user input – File menu should be first item on menu bar– Cut, Copy, Paste should appear on Edit menu


Assigning Shortcut Keys to Menu Items

• Shortcut keys:– Appear to right of menu item– Allow you to select item without opening menu

• Example: Ctrl+S executes Save in MS Word

• Assign shortcut keys to commonly used menu items– Follow Windows standard conventions

• Shortcut keys can be used when menu is closed


Assigning Shortcut Keys to Menu Items (continued)


Figure 8-29: Shortcut key specified in the ShortcutKeys box

Assigning Shortcut Keys to Menu Items (continued)


Figure 8-30: Location of the shortcut key on the menu

Programming with Microsoft Visual Basic 2008 Fourth Edition Chapter Eight String Manipulation.

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