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Microsoft Visual Basic 2010: Reloaded Fourth Edition

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

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Microsoft Visual Basic 2010: Reloaded Fourth Edition

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  1. Microsoft Visual Basic 2010: ReloadedFourth Edition Chapter Ten String Manipulation and Menus

  2. 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

  3. 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

  4. 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

  5. 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

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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. Searching a String • Containsmethod: • 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

  14. 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

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

  16. Figure 10-4: How to search a string (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition 16

  17. 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

  18. 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

  19. 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

  20. Figure 10-6: How to align the characters in a string Microsoft Visual Basic 2010: Reloaded, Fourth Edition 20

  21. 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

  22. 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

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

  24. Figure 10-7: How to use pattern-matching to compare strings (cont'd.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition 24

  25. 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

  26. Adding a Menu to a Form (cont’d.) Figure 10-8: Location of menu elements Microsoft Visual Basic 2010: Reloaded, Fourth Edition 26

  27. 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

  28. 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

  29. 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

  30. 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

  31. Programming Example • Yolanda Drapery Application Figure 10-28: MainForm in the Yolanda Drapery application Microsoft Visual Basic 2010: Reloaded, Fourth Edition 31

  32. 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

  33. 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

  34. 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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