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bsp; Public Sub Display()
Messagebox.Show("Name: " + name + " Age: " + str(age))
End Sub
End Class
Public Class Teacher
Inherits Person
Private salary As Decimal
Public Sub tr_SetValue( ByVal na As String, ByVal a As Integer, ByVal
sa As Decimal)
SetValue(na, a)
salary = sa
End Sub
Public Sub pr()
MyBase.Display()
Messagebox.Show("Salary: " + str(salary))
End Sub
End Class
''''-----------------------------------------------------------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form
Public Sub New()
MyBase.New()
Form1 = Me
''''This call is required by the Win Form Designer.
InitializeComponent()
''''TODO: Add any initialization after the InitializeComponent() call
End Sub
''''Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
........
#End Region
Protected Sub Form1_Click( ByVal sender As Object, ByVal
e As System.EventArgs)
Dim steven As Teacher
steven = New Teacher()
steven.tr_SetValue("Steven", 35, 35000)
steven.pr()
End Sub
End Class
此程序输出如下﹕
Name: Steven Age: 35
Salary: 35000
现在﹐Teacher 类别含有三个资料成员﹕
1. name ──从Person类别继承而来。
2. age ──从Person类别继承而来。
3. salary ──自己定义的。
此外﹐也含有五个程序成员﹕
1. SetValue() ──从Person继承而来。
2. birthYear()──从Person继承而来。
3. Display() ──从Person继承而来。
4. tr_SetValue()──自己定义的。
5. pr()──自己定义的。
由于SetValue()为 Teacher之程序成员﹐所以tr_SetValue()能直接呼叫SetValue()来设定name及age值﹔之后﹐tr_SetValue()自己设定salary之值。同理﹐pr()能直接呼叫 Display()来显示name及age之内容﹔之后﹐pr()自己输出salary之值。也许﹐您会问道﹕子类别自己定义之程序﹐是否能与父类别之程序同名称呢﹖答案是肯定的﹐而且是常见之写法。如果名称相同但是参数不一致（像参数个数不同或参数型态不同），就是父子类别之间的程序多重定义(Procedure Overloading)了，必须写上Overloads字眼。例如﹕上述程序相当于──
''''ex04.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
''''------------------------------------------------------------------------------------------
Class Person
Private name As String
Private age As Integer
Public Sub New()
End Sub
Public Sub SetValue(ByVal na As String, ByVal a As Integer)
name = na
age = a
End Sub
Public Function birthDay() As Integer
birthDay = 2001 - age
End Function
Public Sub Display()
Messagebox.Show("Name: " + name + " Age: " + str(age))
End Sub
End Class
Class Teacher
Inherits Person
Private salary As Decimal
Public Overloads Sub SetValue( ByVal na As String, ByVal a As Integer, ByVal
sa As Decimal)
SetValue(na, a)
salary = sa
End Sub
Public Sub pr()
MyBase.Display()
Messagebox.Show("Salary: " + str(salary))
End Sub
End Class
''''------------------------------------------------------------------------------------------
Public Class Form1
Inherits System.WinForms.Form
Public Sub New()
MyBase.New()
Form1 = Me
''''This call is required by the Win Form Designer.
InitializeComponent()
''''TODO: Add any initialization after the InitializeComponent() call
End Sub
''''Form overrides dispose to clean up the component list.
Public Overrides Sub Dispose()
MyBase.Dispose()
components.Dispose()
End Sub
#Region " Windows Form Designer generated code "
........
#End Region
Protected Sub Form1_Click( ByVal sender As Object, ByVal
e As System.EventArgs)
Dim steven As Teacher
steven = New Teacher()
steven.SetValue("Steven", 35, 35000)
steven.pr()
End Sub
End Class
此程序输出如下﹕
NAME: Steven
AGE : 35
Salary: 35000
此种情况﹐Teacher 类别拥有两个 SetValue()程序﹐一个由Person继承而来﹐一个是自己定义的。同时﹐也拥有两个Display()程序。此时﹐计算机如何分辨它们呢﹖计算机依据程序的参数来决定呼叫那一个程序，当您写成 steven.SetValue("Steven", 35, 35000)时，此SetValue()是子类别自己的SetValue()。而写成SetValue(na,a)时，则是由Person类别继承而来之SetValue()程序。此VB程序已定义如下之类别关系﹕
接下来﹐再为Person定义一个子类别── Student。程序如下﹕
''''ex05.bas
Imports System.ComponentModel
Imports System.Drawing
Imports System.WinForms
''''------------------------------------------------------------------------------------------
Public Class Person
Private name As String
Private age As Integer
Public Sub New()
End Sub
Public Sub SetValue(ByVal na As String, ByVal a As Integer)
name = na
age = a
End Sub
Public Function birthDay() As Integer
birthDay = 2001 - age
End Function
Public Sub Display()
Messagebox.Show("Name: " + name + " Age: " + str(age))
End Sub
End Class
Public Class Teacher
Inherits Person
Private salary As Decimal
Public Overloads Sub SetValue( ByVal na As String, ByVal a As Integer, ByVal
sa As Decimal)
SetValue(na, a)
salary = sa
End Sub
Public Sub pr()
MyBase.Display()
Messagebox.Show("Salary: " + str(salary))
End Sub
End Class
Public Class Student
Inherits Person
Private student_number As Integer
Public Overloads Sub SetValue( ByVal na As String, ByVal a As Integer, ByVal
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