Chapter 8: Manipulating Strings
Programming with Microsoft Visual Basic
.NET, Second Edition
String Manipulation
Lesson A Objectives
• Determine the number of characters contained in
a string
• Remove characters from a string
• Determine whether a string begins or ends with
one or more specific characters
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String Manipulation
Lesson A Objectives (continued)
• Access characters from the beginning, middle,
and end of a string
• Replace one or more characters in a string
• Insert characters within a string
• Search a string for one or more characters
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Manipulating Strings in Visual Basic
.NET
• Many times, an application needs to manipulate
(process) string data
• For example, an application might need to:
– Verify that an inventory part number begins with a
specific letter
– Determine whether the last three characters in an
employee number are valid
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Determining the Number of
Characters Contained in a String
• In many applications, it is necessary to determine
the number of characters contained in a string
• Use a string’s Length property to determine the
number of characters contained in the string
• Syntax of the Length property: string.Length
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Removing Characters from a String
• TrimStart method
– Remove one or more characters from the
beginning of a string
– Syntax: string.TrimStart([trimChars])
• TrimEnd method
– Remove one or more characters from the end of a
string
– Syntax: string.TrimEnd([trimChars])
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Removing Characters from a String
(continued)
• Trim method
– Remove one or more characters from both the
beginning and end of a string
– Syntax: string.Trim([trimChars])
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Removing Characters from a String
(continued)
string.Trim
Removes leading and trailing
spaces
string.Trim(char)
Removes leading and trailing
char
string.TrimStart
Removes leading spaces
string.TrimStart(char) Removes leading char
string.TrimEnd
Removes trailing spaces
string.TrimEnd(char)
Removes trailing char
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The Remove Method
• Use the Remove method to remove one or more
characters located anywhere in a string
• The Remove method returns a string with the
appropriate characters removed
• Syntax: string.Remove(startIndex, count)
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Determining Whether a String Begins
or Ends with a Specific
Sequence of Characters
• StartsWith method
– Determine whether a specific sequence of
characters occurs at the beginning of a string
– Syntax: string.StartsWith(subString)
• EndsWith method
– Determine whether a specific sequence of
characters occurs at the end of a string
– Syntax: string.EndsWith(subString)
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Accessing Characters Contained in a
String
• Use the Substring method to access any number
of characters in a string
• Syntax: string.Substring(startIndex[, count])
• startIndex: the index of the first character you
want to access in the string
• count (optional): specifies the number of
characters you want to access
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Replacing Characters in a String
• Use Replace to replace a sequence of characters
in a string with another sequence of characters
• For example:
– Replace area code “800” with area code “877” in a
phone number
– Replace the dashes in a Social Security number
with the empty string
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Replacing Characters in a String
(continued)
• Syntax: string.Replace(oldValue, newValue)
• oldValue is the sequence of characters that you
want to replace in the string
• newValue is the replacement characters
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The Mid Statement
• Use the Mid statement to replace a specified
number of characters in a string with characters
from another string
• Syntax:
Mid(targetString, start [, count]) = replacementString
• targetString: the string in which you want
characters replaced
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The Mid Statement (continued)
• replacementString: contains the replacement
characters
• start: the character position of the first character
you want replaced in the targetString
• count: the number of characters to replace in the
targetString
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Inserting Characters at the Beginning
and End of a String
• Use the PadLeft and PadRight methods to pad a
string with a character until the string is a
specified length
• PadLeft method pads the string on the left
– Inserts the padded characters at the beginning of
the string and right-aligns the characters in the
string
– Syntax: string.PadLeft(length[, character])
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Inserting Characters at the Beginning
and End of a String (continued)
• PadRight method pads the string on the right
– Inserts the padded characters at the end of the
string and left-aligns the characters in the string
– Syntax: string.PadRight(length[, character])
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Inserting Characters within a String
• Use the Insert method to insert characters within
a string
• For example: insert an employee’s middle initial
within his or her name
• Syntax: string.Insert(startIndex, value)
• startIndex specifies where in the string you want
the value inserted
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Searching a String
• Use the IndexOf method to search a string to
determine whether it contains a specific
sequence of characters
• Syntax: string.IndexOf(value[, startIndex])
• value: the sequence of characters for which you
are searching in the string
• startIndex: the index of the character at which the
search should begin
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Searching a String (continued)
• For example:
– Determine if the area code “312” appears in a
phone number
– Determine if the street name “Elm Street” appears
in an address
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Searching a String (continued)
Figure 8-13: String manipulation techniques
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Searching a String (continued)
Figure 8-13: String manipulation techniques (continued)
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Using a Main Menu Control
Lesson B Objectives
• Add a main menu control to a form
• Add menu elements to a main menu control
• Assign access keys and shortcut keys to menu
elements
• Code a menu item’s Click event procedure
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Completing the Hangman Game
Application’s User Interface
• You will create a simplified version of the
Hangman game for Mr. Mitchell, who teaches
second grade at Hinsbrook School
• In this lesson, you will:
– Complete the application’s user interface
– Begin coding the application
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Completing the Hangman Game
Application’s User Interface
(continued)
Figure 8-14: Partially completed interface for the Hangman
Game application
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Adding a Main Menu Control to a
Form
• Use a main menu control to include one or more
menus in an application
• Each menu contains a menu title, which appears
on the menu bar at the top of a Windows form
• When you click a menu title, its corresponding
menu opens and displays a list of options, called
menu items
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Adding a Main Menu Control to a
Form (continued)
• The menu items can be commands, separator
bars, or submenu titles
• Clicking a command on a menu executes the
command
• Clicking a submenu title opens an additional
menu of options
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Adding a Main Menu Control to a
Form (continued)
Figure 8-15: Location of menu elements
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Adding a Main Menu Control to a
Form (continued)
• Each option on a submenu is referred to as a
submenu item
• The purpose of a separator bar is to visually
group together the related items on a menu or
submenu
• Each menu element is considered an object and
has a set of properties associated with it
• The most commonly used properties for a menu
element are the Name and Text properties
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Assigning Shortcut Keys
• Shortcut keys
– Appear to the right of a menu item
– Allow you to select an item without opening the
menu
• You should assign shortcut keys only to
commonly used menu items
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Assigning Shortcut Keys (continued)
Figure 8-19: Shortcut key displayed on the File menu
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Coding the Click Event Procedure for
the Exit Menu Item
• When the user clicks the Exit item on the File
menu, the item’s Click event procedure should
end the Hangman Game application
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Completing the Hangman Game
Application
Lesson C Objectives
• Include the Substring method in a procedure
• Include the Mid statement in a procedure
• Include the IndexOf method in a procedure
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The Hangman Game Application
• An application that two students can use to play
a simplified version of the Hangman game on the
computer
• The application should allow one of the students
to enter a five-letter word, and then allow the
other student to guess the word, letter by letter
• The game is over when the second student
either guesses all of the letters in the word or
makes 10 incorrect guesses, whichever comes
first
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The Hangman Game Application
(continued)
Figure 8-22: Hangman Game application’s user interface
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Coding the Click Event Procedure for
the uiFileNewMenuItem
• Each time the user wants to begin a new
Hangman game, he or she will need to:
– Click File on the application’s menu bar
– Click New Game
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Coding the Click Event Procedure for
the uiFileNewMenuItem (continued)
Figure 8-24: Pseudocode for the uiFileNewMenuItem’s Click
event procedure
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Coding the Click Event Procedure for
the uiFileNewMenuItem (continued)
Figure 8-24: Pseudocode for the uiFileNewMenuItem’s Click
event procedure (continued)
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Summary
• To determine the number of characters contained
in a string, use the Length property in the
following syntax: string.Length
• To remove one or more characters from
anywhere in a string, use the Remove method
• Use the StartsWith method to determine whether
a string begins with a specific sequence of
characters
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Summary (continued)
• Use the EndsWith method to determine whether
a string ends with a specific sequence of
characters
• To access one or more characters contained in a
string, use the Substring method
• To insert characters within a string, use the Insert
method
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Summary (continued)
• To search a string to determine whether it
contains a specific sequence of characters, use
the IndexOf method
• To add a main menu control to a form, use the
MainMenu tool in the toolbox
• To assign a shortcut key to a menu item, set the
menu item’s Shortcut property
• To replace a character in a string with another
character, use the Mid statement
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