Designing, Creating, and Using a Class

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Chapter 9

• Designing, Creating, and Using a Class

2
Objectives

• Understand when to create a class when designing
  a solution
• Design a class using the UML
• Create a new class in Visual Basic .NET
• Create a constructor for a class
• Create a property for a class
• Code a Get property procedure

3
Objectives

• Code a Set property procedure
• Create a method for a class
• Create a class by using inheritance
• Draw a UML object diagram for an object
• Use a class in a Visual Basic .NET program

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Program Development
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Program Development
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Program Development
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Program Development
8
Starting Visual Basic .NET and Starting a Class
Library Project

• Insert the Data Disk in drive A
• Start Visual Basic .NET. When the Start Page
  appears, click the New Project button on the
  Start Page
• When the New Project dialog box appears, click
  the Class Library icon in the Templates area.
  Double-click the text, ClassLibrary1, in the Name
  box. Type Compensation Review in the Name box
• Click the Browse button. If necessary, click 3½
  Floppy (A) in the Look in box. Click Chapter9
  and then click the Open button
• Click the OK button and Maximize the Visual Basic
  .NET window. If necessary, close the Output
  window

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Declaring Private Variables in a Class

• Right-click the Class1.vb class in the Solution
  Explorer window. Click the Rename command on the
  shortcut menu, type Employee.vb as the new module
  name, and then press the ENTER key
• If necessary, right-click the Employee.vb class
  in the Solution Explorer window and then click
  the View Code command on the shortcut menu
• Enter Option Strict On as the first line of code
  in the code window. Replace the class name,
  Class1, by typing the class name, Employee, on
  line 2
• Type lines 3 through 10 as shown on the following
  slide

10
Declaring Private Variables in a Class
11
Creating a Constructor for a Class

• Enter lines 12 through 20, as shown below

12
Adding a Property to a Class
13
Coding a Get Property Procedure
14
Adding a Property to a Class and Coding a Get
Property Procedure

• Enter line 23, followed by line 25, as shown
  below

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Coding a Set Property Procedure
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Coding a Set Property Procedure

• Change the variable name, Value, to intEmployeeID
  on line 27
• Enter line 28 as shown below

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Coding the Remaining Properties

• Unpin the Toolbox window from the main work area
  in order to display more code in the main work
  area. Enter lines 32 through 93 as shown on the
  following slide

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Coding a Method for a Class

• Enter lines 95 through 100 as shown below

20
Adding a Class to a Class Library

• Right-click the Compensation Review project in
  the Solution Explorer window. When the shortcut
  menu appears, point to the Add command
• Click the Add Class command on the Add menu.
  When the Add New Item Compensation Review
  dialog box appears, select the Class1.vb text in
  the Name box and type HourlyEmployee.vb as the
  new name
• Click the Open button

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Adding a Class to a Class Library
22
Inheriting from a Base Class
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Inheriting from a Base Class

• Enter Option Strict On as the first line of code
  in the code window. Click line 3 and then type
  the line of code shown below

24
Creating a Private Variable for a Property in a
Subclass

• Enter line 5 as shown below

25
Creating a Constructor and a Property in a
Subclass

• Type lines 7 through 10, 12, and 14-17, as shown
  below

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Creating an Additional Subclass

• Right-click the Compensation Review project in
  the Solution Explorer window. When the shortcut
  menu appears, click the Add command
• Click the Add Class command on the Add menu.
  When the Add New Item Compensation Review
  dialog box appears, select the Class1.vb text in
  the Name box and type SalariedEmployee.vb as the
  new name
• Click the Open button. When the
  SalariedEmployee.vb code window appears, enter
  the code on the following slide

27
Creating an Additional Subclass
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Building, Saving, and Documenting the Class
Library

• Right-click the Compensation Review project in
  the Solution Explorer window. When the shortcut
  menu appears, click the Build command
• Click the Employee.vb tab and then use the Print
  command on the File menu to print a record of the
  code for the Employee class
• Click the HourlyEmployee.vb tab and then use the
  Print command on the File menu to print a record
  of the code for the HourlyEmployee class
• Click the SalariedEmployee.vb tab and then use
  the Print command on the File menu to print a
  record of the code for the SalariedEmployee class
• Click the Close Solution command on the File menu
  to close the Compensation Review solution

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Using a Class in Code
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Starting a New Project and Creating the User
Interface

• If necessary, click the Show Start Page command
  on the Help menu. When the Start Page appears,
  click the New Project button on the Start Page
• When the New Project dialog box appears, if
  necessary, click Create directory for Solution.
  Click the Windows Application icon in the
  Templates area. Double-click the text,
  WindowsApplication1, in the Name box. Type
  EmployeeClassTest in the Name box
• Click the Browse button. If necessary, click 3½
  Floppy (A) in the Look in box. Click Chapter9
  and then click the Open button

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Starting a New Project and Creating the User
Interface

• Click the OK button. If necessary, close the
  Output window
• With Form1 selected, set the properties of the
  Form1 form as specified on the following slide

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Starting a New Project and Creating the User
Interface
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Starting a New Project and Creating the User
Interface

• Add and then set the property values of the
  controls as listed in Table 9-9 on pages VB 9.54
  through VB 9.57. Add the three RadioButton
  controls to the first GroupBox control. Add the
  TextBox control and the two NumericUpDown
  controls to the second GroupBox control, as shown
  on the following slide

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Starting a New Project and Creating the User
Interface
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Adding a Reference to a Class

• Double-click the Employee Object radio button on
  the Form1 form. When Visual Basic .NET creates
  the radEmployeeObject_CheckedChanged event
  procedure, right-click the References folder in
  the Solution Explorer window
• Click the Add References command on the
  References shortcut menu
• Click the Browse button
• Use the Look in box to navigate to the
  A\Chapter9\Compensation Review\Compensation
  Review\bin folder. If necessary, click the
  Compensation Review.dll component to select it
• Click the Open button

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Adding a Reference to a Class

• Click the OK button. If necessary, expand the
  References folder to view the references in the
  EmployeeClassTest project

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Importing a Namespace
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Importing a Namespace

• Enter line 1 of the code as shown below. Type
  the keyword, Imports, followed by a space
• Double-click Compensation_Review

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Creating Objects from Classes

• Type the first four words of line 196 as shown
  below, followed by a space. If necessary, scroll
  the Intellisense list to the Employee keyword
• Double-click Employee. Enter lines 197 and 198
  as shown below

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Getting Property Values of an Object in Code

• Enter lines 201 through 207 as shown on the
  following slide
• Click the Form1.vbDesign tab in the main work
  area. Double-click the HourlyEmployee Object
  radio button on the Form1 form. When Visual
  Basic .NET creates the radHourlyEmployeeObject_Che
  ckedChanged event procedure, enter lines 211-217
  as shown on the following slide
• Click the Form1.vbDesign tab in the main work
  area. Double-click the SalariedEmployee Object
  radio button on the Form1 form. When Visual
  Basic .NET creates the radSalariedEmployeeObject_C
  heckedChanged event procedure, enter lines
  221-227 as shown on the following slide

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Getting Property Values from an Object in Code
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Setting Property Values of an Object in Code

• Click the Form1.vbDesign tab in the main work
  area. Double-click the Set Properties button on
  the Form1 form. When Visual Basic .NET creates
  the btnSetProperties_Click event procedure, enter
  lines 231 through 240 as shown on the following
  slide

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Setting Property Values of an Object in Code
44
Saving and Testing the Project

• Click the Save All button on the Standard toolbar
• Click the Start button on the Visual Basic .NET
  Standard toolbar. When the EmployeeClassTest
  application starts, minimize the Visual Basic
  .NET window. Type Sandy Grant in the Name text
  box in the EmployeeClassTest application window
  and then click the Set Properties button
• Click the HourlyEmployee Object radio button.
  Type Randolph Jefferson in the Name text box.
  Type 10.25 as the Hourly rate. Click the Set
  Properties button
• Click the Employee Object radio button
• Type Emerson Grant in the Name box and click the
  Set Properties button

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Saving and Testing the Project

• Click the SalariedEmployee Object radio button.
  Type Lisa Land as the Name and type 75,500 as the
  Annual Salary. Click the Set Properties button
• Continue changing the properties of the three
  objects and making certain that the proper values
  appear as each radio button is selected, until
  you are satisfied that the application works as
  designed and you understand how the objects and
  properties relate to what is displayed on the
  screen
• Click the Close button on the EmployeeClassTest
  application window title bar. If necessary,
  click the Visual Basic .NET taskbar button to
  display the Visual Basic .NET window. If
  necessary, close the Output window

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Documenting the Application and Quitting Visual
Basic .NET

• Click the Form1.vb Design tab, and then use the
  PRINT SCREEN key to print a record of the user
  interface design of the Form1 form
• Click the Form1.vb tab. Click File on the menu
  bar and then click Page Setup
• When the Page Setup dialog box appears, if
  necessary, click Line numbers and then click the
  OK button
• Use the Print command on the File menu to print a
  record of the code for the EmployeeClassTest
  application
• Click the Visual Basic .NET Close button

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Summary

• Understand when to create a class when designing
  a solution
• Design a class using the UML
• Create a new class in Visual Basic .NET
• Create a constructor for a class
• Create a property for a class
• Code a Get property procedure

48
Summary

• Code a Set property procedure
• Create a method for a class
• Create a class by using inheritance
• Draw a UML object diagram for an object
• Use a class in a Visual Basic .NET program

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Chapter 9 Complete