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					Microsoft Visual Basic 2010:
         Reloaded
          Fourth Edition


           Chapter Ten
  String Manipulation and Menus
                                    Objectives

After studying this chapter, you should be able to:
• Determine the number of characters in a string
• Remove characters from a string
• Insert characters in a string
• Search a string
• Access the characters in a string




Microsoft Visual Basic 2010: Reloaded, Fourth Edition
                        Objectives (cont’d.)

•   Align the characters in a string
•   Compare strings using pattern-matching
•   Add a menu to a form
•   Code a menu item’s Click event procedure




Microsoft Visual Basic 2010: Reloaded, Fourth Edition
                       Working with Strings

• Most applications need to manipulate string data in
  some way
• String properties and methods are used to
  manipulate string data




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   4
Determining the Number of Characters
              in a String
• Length property: stores the number of characters
  contained in a string as an integer value
     – Can be used with a String variable, a String named
       constant, or the Text property of a control




Microsoft Visual Basic 2010: Reloaded, Fourth Edition       5
   Figure 10-1: How to determine the number of characters in a string
Microsoft Visual Basic 2010: Reloaded, Fourth Edition                   6
    Removing Characters from a String

• Computer first makes a temporary copy of the
  string in memory and operates on the copy only
• Trim method: removes one or more spaces from
  both the beginning and end of a string
• Remove method: removes a specified number of
  characters located anywhere in a string
• Index: an integer indicating the character’s position
  in the string
     – The first character in a string has an index of 0


Microsoft Visual Basic 2010: Reloaded, Fourth Edition      7
    Removing Characters from a String
               (cont’d.)
• Arguments:
     – startIndex argument: the index of the first character
       to be removed
     – numCharsToRemove argument: number of
       characters to be removed
           • If omitted, all characters from the startIndex position
             through the end of the string are removed




Microsoft Visual Basic 2010: Reloaded, Fourth Edition                  8
    Removing Characters from a String
               (cont’d.)




        Figure 10-2: How to remove characters from a string
Microsoft Visual Basic 2010: Reloaded, Fourth Edition         9
    Removing Characters from a String
               (cont’d.)




          Figure 10-2: How to remove characters from a string (cont’d.)


Microsoft Visual Basic 2010: Reloaded, Fourth Edition                     10
         Inserting Characters in a String
• Insert method: used to insert characters
  anywhere within a string
• Computer makes and operates on a temporary copy
  of the string
• Arguments:
   – startIndex: specifies where in the string to insert the
     value
   – value: the character(s) to be inserted




Microsoft Visual Basic 2010: Reloaded, Fourth Edition          11
         Inserting Characters in a String
                    (cont’d.)




                   Figure 10-3: How to insert characters in a string
Microsoft Visual Basic 2010: Reloaded, Fourth Edition                  12
                         Searching a String
• Contains method:
     – Determines if a string contains a specific sequence
       of characters
     – Returns a Boolean value of True when the substring
       is contained in the string, and False if not
     – Performs a case-sensitive search
• Arguments:
     – subString: represents the sequence of characters to
       be searched for


Microsoft Visual Basic 2010: Reloaded, Fourth Edition    13
              Searching a String (cont’d.)
• IndexOf method: returns an integer representing
  the location of a substring within a string
     – Performs a case-sensitive search
• Arguments:
     – subString: sequence of characters to be searched
       for
     – startIndex: the starting position for the search (zero-
       relative)




Microsoft Visual Basic 2010: Reloaded, Fourth Edition        14
Figure 10-4:
How to search
a string




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   15
Figure 10-4:
How to search
a string (cont’d.)




  Microsoft Visual Basic 2010: Reloaded, Fourth Edition   16
                Accessing the Characters
                       in a String
• Substring method: accesses any number of
  characters contained in a string
• Arguments:
     – startIndex: index of the first character to be accessed
       (zero-relative)
     – numCharsToAccess: number of characters to be
       accessed




Microsoft Visual Basic 2010: Reloaded, Fourth Edition       17
                Accessing the Characters
                   in a String (cont’d.)




            Figure 10-5: How to access characters in a string
Microsoft Visual Basic 2010: Reloaded, Fourth Edition           18
      Aligning the Characters in a String
• PadLeft method: inserts characters at the
  beginning of a string
• PadRight method: inserts characters at the end
  of a string
• Arguments:
     – totalChars: represents the total number of characters
       you want in the resulting string
     – padCharacter: the character used to pad the string;
       default value is the space character


Microsoft Visual Basic 2010: Reloaded, Fourth Edition     19
Figure 10-6:
How to align
the characters
in a string




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   20
                   Using Pattern-Matching
                    to Compare Strings
• Like operator:
     – Uses pattern-matching characters to determine if
       one string is equal to another
     – Returns a Boolean value (True/False)
• Arguments:
     – pattern: contains one or more pattern-matching
       characters
     – characterList: a listing of characters to be matched




Microsoft Visual Basic 2010: Reloaded, Fourth Edition         21
                   Using Pattern-Matching
                    to Compare Strings
• Pattern-matching characters:
     – ? Represents 1 character only
     – * represents 0 or more characters
     – # represents a single digit
• Use square brackets [ ] to provide a list of
  characters to match
     – Use a hyphen between characters to specify a range
       of characters



Microsoft Visual Basic 2010: Reloaded, Fourth Edition   22
  Figure 10-7: How
  to use pattern-
  matching to
  compare strings




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   23
Figure 10-7: How to use
pattern-matching to
compare strings (cont'd.)




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   24
                 Adding a Menu to a Form

• Menu strip control: used to include one or more
  menus on a Windows form
     – Found in the Menus & Toolbars section of the
       toolbox
• Menu title: appears on the menu bar at the top of
  the form
     – When clicked, the menu opens and displays a list of
       options called menu items
• Clicking a menu item executes the command
  associated with it

Microsoft Visual Basic 2010: Reloaded, Fourth Edition    25
      Adding a Menu to a Form (cont’d.)




             Figure 10-8: Location of menu elements




Microsoft Visual Basic 2010: Reloaded, Fourth Edition   26
      Adding a Menu to a Form (cont’d.)

• Each menu element is considered an object
     – Each has a set of properties associated with it
• Name property: used to refer to the menu element
  in code
• Text property: stores the menu element’s caption
  – the text the user sees
• Access key: used in combination with the Alt key,
  will open the menu
• Shortcut key: allows the user to select the item
  without opening the menu
Microsoft Visual Basic 2010: Reloaded, Fourth Edition    27
      Adding a Menu to a Form (cont’d.)




                             Figure 10-9: Game menu




           Figure 10-10: Exit command’s Click event procedure

Microsoft Visual Basic 2010: Reloaded, Fourth Edition           28
                   Programming Tutorial 1
• Creating the Guess the Word Game Application




        Figure 10-12: MainForm in the Guess the Word Game application

Microsoft Visual Basic 2010: Reloaded, Fourth Edition                   29
                   Programming Tutorial 2
• Creating the Bucky Burgers Application




           Figure 10-22: MainForm for the Bucky Burgers application

Microsoft Visual Basic 2010: Reloaded, Fourth Edition                 30
                    Programming Example
• Yolanda Drapery Application




          Figure 10-28: MainForm in the Yolanda Drapery application



Microsoft Visual Basic 2010: Reloaded, Fourth Edition                 31
                                     Summary

• Use a menu strip control to add one or more
  menus to a form
• Menu elements should have access keys
• String manipulation techniques:
     –   Length property: number of characters in the string
     –   Trim method: removes leading and trailing spaces
     –   Remove method: removes characters from a string
     –   Insert method: inserts characters into a string



Microsoft Visual Basic 2010: Reloaded, Fourth Edition      32
                          Summary (cont'd.)
• String manipulation techniques (cont’d.):
     – Contains method: determines whether a specific
       sequence of characters appears in a string; returns a
       Boolean value
     – IndexOf method: determines whether a specific
       sequence of characters appears in a string; returns
       the integer position where the sequence starts
     – Substring method: accesses one or more characters
       in a string



Microsoft Visual Basic 2010: Reloaded, Fourth Edition     33
                          Summary (cont'd.)
• String manipulation techniques (cont’d.):
     – PadLeft method: pads the beginning of a string with
       the specified character
     – PadRight method: pads the end of a string with the
       specified character
     – Like operator: uses pattern-matching to compare
       strings




Microsoft Visual Basic 2010: Reloaded, Fourth Edition        34

				
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