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 3Programming with Microsoft Visual Basic 2008, Fourth Edition

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 4Programming with Microsoft Visual Basic 2008, Fourth Edition

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 5Programming with Microsoft Visual Basic 2008, Fourth Edition

Replacing Characters in a String (continued) 6Programming with Microsoft Visual Basic 2008, Fourth Edition Figure 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 7Programming with Microsoft Visual Basic 2008, Fourth Edition

The Mid Statement (continued) 8Programming with Microsoft Visual Basic 2008, Fourth Edition 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 9Programming with Microsoft Visual Basic 2008, Fourth Edition

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 10Programming with Microsoft Visual Basic 2008, Fourth Edition

Insert Method (continued) 11Programming with Microsoft Visual Basic 2008, Fourth Edition 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 12Programming with Microsoft Visual Basic 2008, Fourth Edition

Accessing Characters Contained in a String (continued) 13Programming with Microsoft Visual Basic 2008, Fourth Edition 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 14Programming with Microsoft Visual Basic 2008, Fourth Edition

Using Pattern-Matching to Compare Strings (continued) 15Programming with Microsoft Visual Basic 2008, Fourth Edition 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 16Programming with Microsoft Visual Basic 2008, Fourth Edition

Adding a Menu to a Form (continued) 17Programming with Microsoft Visual Basic 2008, Fourth Edition 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 18Programming with Microsoft Visual Basic 2008, Fourth Edition

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 19Programming with Microsoft Visual Basic 2008, Fourth Edition

Assigning Shortcut Keys to Menu Items (continued) 20Programming with Microsoft Visual Basic 2008, Fourth Edition Figure 8-29: Shortcut key specified in the ShortcutKeys box

Assigning Shortcut Keys to Menu Items (continued) 21Programming with Microsoft Visual Basic 2008, Fourth Edition Figure 8-30: Location of the shortcut key on the menu