1. Multiple Classes and Inheritance
CHAPTER ELEVEN
Multiple Classes and Inheritance

2. Objectives Use the TabIndex Property
Edit input, including MaskedTextBox,TextBox, and ComboBox objects
Describe the three-tiered program structure
Understand a class
Create a class
Chapter 11: Multiple Classes and Inheritance
© 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

3. Objectives Instantiate an object
Pass arguments when instantiating an object
Write a class constructor
Call a procedure in a separate class
Chapter 11: Multiple Classes and Inheritance
© 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

4. Objectives Code a base class and a subclass to incorporate inheritance
Call procedures found in a base class and a subclass
Write overridable and overrides procedures
Create and write a comma-delimited text file
Chapter 11: Multiple Classes and Inheritance

5. Use the TabIndex Property in the User Interface
Select the object that will be selected when program execution begins. Scroll in the Properties window until the TabIndex property is visible and then double-tap or double-click in the right column of the TabIndex property
Type 1 and then press the ENTER key
Select the object which should be selected when the user presses the TAB key. Double-tap or double-click the right column of the TabIndex property for the object, type 2 and then press the ENTER key
Chapter 11: Multiple Classes and Inheritance

6. Use the TabIndex Property in the User Interface
Chapter 11: Multiple Classes and Inheritance

7. Editing Input Data
Student ID: The Student ID object is a masked text box, and the mask is for the Social Security number in the same layout, so the mask ensures that the user can enter only numbers. However, the Social Security mask does not ensure that the user enters all nine numbers. Therefore, a check must be included in the program to require the user to enter all nine numeric digits
Student Name: The program must ensure that the user enters characters in this TextBox object. In addition, spaces cannot be entered instead of actual alphabetic characters
Number of Units: The user must enter a numeric value from 1 through 24 for the number of units the student is taking
Major: The user must select a major from the list in the Major ComboBox object
Chapter 11: Multiple Classes and Inheritance

8. Editing Input Data
Chapter 11: Multiple Classes and Inheritance

9. Program Structure Using Classes
The concept of separating processing and hiding data within specific classes is called encapsulation
When developing programs with multiple classes, a starting point for determining what classes should appear in a program is the three-tier program structure
Chapter 11: Multiple Classes and Inheritance

10. Program Structure Using Classes
The presentation tier contains the classes that display information for the user and accept user input
The business tier contains the logic and calculations that must occur in order to fulfill the requirements of the program
The persistence tier, sometimes called the data access tier, contains the code required to read and write data from permanent storage
Chapter 11: Multiple Classes and Inheritance

11. Sample Program Classes
Presentation tier: The presentation tier contains the frmCollege class. This class displays the user interface in a Windows Form object and edits the user input data to ensure its validity
Business tier: The business tier contains two classes: the Student class and the OnCampusStudent class. The Student class contains data for each registered student and calculates the registration costs for some students. The OnCampusStudent class is used for registered students who live in on-campus residence halls
Persistence tier: The persistence tier consists of one class, StudentCostsFile, which creates and writes the Student Costs File
Chapter 11: Multiple Classes and Inheritance

12. Creating a Class
With Visual Studio open and a new Windows Application project started, press and hold or right-click the project name in the Solution Explorer window and then point to Add on the shortcut menu
Tap or click Class on the Add submenu
In the Name text box, type Student as the name of the class and then tap or click the Add button
Using the same techniques, create the OnCampusStudent class and the StudentCostsFile class
Chapter 11: Multiple Classes and Inheritance

13. Creating a Class
Chapter 11: Multiple Classes and Inheritance

14. Instantiating a Class and Class Communication
A class acts as a template for an object
Chapter 11: Multiple Classes and Inheritance

15. Constructors in New Instantiated Classes
When a class is instantiated into an object using the New keyword, a special procedure called a constructor is executed in the class
The constructor prepares the object for use in the program
Chapter 11: Multiple Classes and Inheritance

16. Passing Arguments when Instantiating an Object
When you instantiate an object, data often must be passed to the object
In the Student class, the New statement must be written with corresponding arguments; that is, the “signature” of the instantiating statement must be the same as the constructor heading in the class
Chapter 11: Multiple Classes and Inheritance

17. Passing Arguments when Instantiating an Object
Chapter 11: Multiple Classes and Inheritance

18. Calling a Procedure in a Separate Class
Most of the time, separate classes in a program contain procedures that must be executed
Chapter 11: Multiple Classes and Inheritance

19. Inheritance
Inheritance allows one class to inherit attributes and procedures from another class
Chapter 11: Multiple Classes and Inheritance

20. Inheritance
Chapter 11: Multiple Classes and Inheritance

21. Inheritance
Chapter 11: Multiple Classes and Inheritance

22. Base Class Constructor
Chapter 11: Multiple Classes and Inheritance

23. Subclass Constructor
Chapter 11: Multiple Classes and Inheritance

24. Inheritance and Procedures
When using inheritance, the subclass can use the procedures within the base class as well as its variables
Between the base class and the subclass, five different techniques can be used for referencing and calling a procedure from an outside class such as a Form class
After the base class and the subclass have been instantiated, the following techniques are available:
Chapter 11: Multiple Classes and Inheritance

25. Inheritance and Procedures
Base Class
Call a named procedure in the base class
Call an Overridable procedure in the base class
Subclass
Call an Overridable Procedure in the subclass
Call a named procedure in the subclass
Call a base class procedure in the subclass
Chapter 11: Multiple Classes and Inheritance

26. Call a Named Procedure in the Base Class
Chapter 11: Multiple Classes and Inheritance

27. Calling an Overridable Procedure in a Base Class
Need 11-30b
Chapter 11: Multiple Classes and Inheritance

28. Calling an Overridable Procedure in a Subclass
Chapter 11: Multiple Classes and Inheritance

29. Calling a Named Procedure in the Subclass
Chapter 11: Multiple Classes and Inheritance

30. Calling a Base Class Procedure in the Subclass
Chapter 11: Multiple Classes and Inheritance

31. Persistence Classes
The persistence tier in an application, sometimes called the data access tier, contains classes that are involved in saving and retrieving data stored on a permanent storage medium, such as a hard disk or a USB drive
Chapter 11: Multiple Classes and Inheritance

32. Persistence Classes
Chapter 11: Multiple Classes and Inheritance

33. Comma-Delimited Text File
Chapter 11: Multiple Classes and Inheritance

34. Comma-Delimited Text File
Chapter 11: Multiple Classes and Inheritance

35. Program Design
Chapter 11: Multiple Classes and Inheritance

36. Program Design
Chapter 11: Multiple Classes and Inheritance

37. Program Design
Chapter 11: Multiple Classes and Inheritance

38. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

39. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

40. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

41. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

42. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

43. Event Planning Document
Chapter 11: Multiple Classes and Inheritance

44. Summary Use the TabIndex Property
Edit input, including MaskedTextBox,TextBox, and ComboBox objects
Describe the three-tiered program structure
Understand a class
Create a class
Chapter 11: Multiple Classes and Inheritance
© 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

45. Summary Instantiate an object
Pass arguments when instantiating an object
Write a class constructor
Call a procedure in a separate class
Chapter 11: Multiple Classes and Inheritance
© 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

46. Summary Code a base class and a subclass to incorporate inheritance
Call procedures found in a base class and a subclass
Write overridable and overrides procedures
Create and write a comma-delimited text file
Chapter 11: Multiple Classes and Inheritance

47. CHAPTER ELEVEN COMPLETE
Multiple Classes and Inheritance