VB.Net/Class/Polymorphism

Demonstrate polymorphism in Point-Circle-Cylinder hierarchy

Imports System
Public Class MainClass
    Shared Sub Main(ByVal args As String())
      " instantiate Point, Circle and Cylinder objects
      Dim point As New Point(7, 11)
      Dim circle As New Circle(22, 8, 3.5)
      Dim cylinder As New Cylinder(10, 10, 3.3, 10)
      " instantiate array of base-class references
      Dim arrayOfShapes As CShape() = New CShape(2) {}
      " arrayOfShapes(0) refers to Point object
      arrayOfShapes(0) = point
      " arrayOfShapes(1) refers to Circle object
      arrayOfShapes(1) = circle
      " arrayOfShapes(2) refers to Cylinder object
      arrayOfShapes(2) = cylinder
      Console.WriteLine( point.Name & ": " & _
         point.ToString() & vbCrLf & circle.Name & ": " & _
         circle.ToString() & vbCrLf & cylinder.Name & _
         ": " & cylinder.ToString() )
      Dim shape As CShape
      For Each shape In arrayOfShapes
         Console.WriteLine( vbCrLf & vbCrLf & shape.Name & ": " & _
            shape.ToString() & vbCrLf & "Area = " & _
            String.Format("{0:F}", shape.Area) & vbCrLf & _
            "Volume = " & String.Format("{0:F}", shape.Volume) )
      Next
    End Sub
End Class
Public MustInherit Class CShape
   " return shape area
   Public Overridable Function Area() As Double
      Return 0
   End Function " Area
   " return shape volume
   Public Overridable Function Volume() As Double
      Return 0
   End Function " Volume
   " overridable method that should return shape name
   Public MustOverride ReadOnly Property Name() As String
End Class " CShape

Public Class Circle
   Inherits Point " Circle Inherits from class Point
   Private mRadius As Double
   " default constructor
   Public Sub New()
      " implicit call to Point constructor occurs here
      Radius = 0
   End Sub " New
   " constructor
   Public Sub New(ByVal xValue As Integer, _
      ByVal yValue As Integer, ByVal radiusValue As Double)
      " use MyBase reference to Point constructor explicitly
      MyBase.New(xValue, yValue)
      Radius = radiusValue
   End Sub " New
   " property Radius
   Public Property Radius() As Double
      Get
         Return mRadius
      End Get
      Set(ByVal radiusValue As Double)
         If radiusValue >= 0 Then " mRadius must be nonnegative
            mRadius = radiusValue
         End If
      End Set
   End Property " Radius
   " calculate Circle diameter
   Public Function Diameter() As Double
      Return mRadius * 2
   End Function " Diameter
   " calculate Circle circumference
   Public Function Circumference() As Double
      Return Math.PI * Diameter()
   End Function " Circumference
   " calculate Circle area
   Public Overrides Function Area() As Double
      Return Math.PI * mRadius ^ 2
   End Function " Area
   " return String representation of Circle
   Public Overrides Function ToString() As String
      " use MyBase to return Circle String representation
      Return "Center= " & MyBase.ToString() & _
         "; Radius = " & mRadius
   End Function " ToString
   " override property Name from class Point
   Public Overrides ReadOnly Property Name() As String
      Get
         Return "Circle"
      End Get
   End Property " Name
End Class
Public Class Cylinder
   Inherits Circle " Cylinder inherits from class Circle
   Private mHeight As Double
   " default constructor
   Public Sub New()
      " implicit call to Circle constructor occurs here
      Height = 0
   End Sub " New
   " four-argument constructor
   Public Sub New(ByVal xValue As Integer, _
      ByVal yValue As Integer, ByVal radiusValue As Double, _
      ByVal heightValue As Double)
      " explicit call to Circle constructor
      MyBase.New(xValue, yValue, radiusValue)
      Height = heightValue " set Cylinder height
   End Sub " New
   " property Height
   Public Property Height() As Double
      Get
         Return mHeight
      End Get
      " set Cylinder height if argument value is positive
      Set(ByVal heightValue As Double)
         If heightValue >= 0 Then " mHeight must be nonnegative
            mHeight = heightValue
         End If
      End Set
   End Property " Height
   " override method Area to calculate Cylinder surface area
   Public Overrides Function Area() As Double
      Return 2 * MyBase.Area + MyBase.Circumference * mHeight
   End Function " Area
   " calculate Cylinder volume
   Public Overrides Function Volume() As Double
      Return MyBase.Area * mHeight
   End Function " Volume
   " convert Cylinder to String
   Public Overrides Function ToString() As String
      Return MyBase.ToString() & "; Height = " & mHeight
   End Function " ToString
   " override property Name from class Circle
   Public Overrides ReadOnly Property Name() As String
      Get
         Return "Cylinder"
      End Get
   End Property " Name
End Class 
Public Class Point
   Inherits CShape " Point inherits from MustInherit class CShape
   " point coordinate
   Private mX, mY As Integer
   " default constructor
   Public Sub New()
      " implicit call to Object constructor occurs here
      X = 0
      Y = 0
   End Sub " New
   " constructor
   Public Sub New(ByVal xValue As Integer, _
      ByVal yValue As Integer)
      " implicit call to Object constructor occurs here
      X = xValue
      Y = yValue
   End Sub " New
   " property X
   Public Property X() As Integer
      Get
         Return mX
      End Get
      Set(ByVal xValue As Integer)
         mX = xValue " no need for validation
      End Set
   End Property " X
   " property Y 
   Public Property Y() As Integer
      Get
         Return mY
      End Get
      Set(ByVal yValue As Integer)
         mY = yValue " no need for validation
      End Set
   End Property " Y
   " return String representation of Point
   Public Overrides Function ToString() As String
      Return "[" & mX & ", " & mY & "]"
   End Function " ToString
   " implement MustOverride property of class CShape
   Public Overrides ReadOnly Property Name() As String
      Get
         Return "Point"
      End Get
   End Property " Name
End Class

PolyMorphism At Work

Imports System
Imports System.Collections

Public Class MainClass
  Shared Sub Main()
     Dim e1 As New Employee("Employee", 5)
     Dim e2 As New Programmer("Programmer", 15)
     Dim e3 As New Archictect("Archictect", 15)
     Dim ourEmployees(2) As Employee
    
     ourEmployees(0) = e1
     ourEmployees(1) = e2
     ourEmployees(2) = e3
    
     Dim anEmployee As Employee
     For Each anEmployee In ourEmployees
       anEmployee.RaiseSalary(0.1D)
       Console.WriteLine(anEmployee.TheName & " salary now is " & anEmployee.Salary())
    Next
  End Sub
  
End Class
Public Class Employee
  Private m_Name As String
  Private m_Salary As Decimal
  Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
    m_Name = TheName
    m_Salary = curSalary
  End Sub
  Public ReadOnly Property TheName() As String
    Get
      Return m_Name
    End Get
  End Property
  Public ReadOnly Property Salary() As Decimal
    Get
      Return MyClass.m_Salary
    End Get
  End Property
  Public Overridable Overloads Sub RaiseSalary(ByVal Percent As Decimal)
      m_Salary = (1 + Percent) * m_Salary
  End Sub
End Class
Public Class Programmer
  Inherits Employee
  Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
    MyBase.New(theName, curSalary)
  End Sub
  Public Overloads Overrides Sub RaiseSalary(ByVal Percent As Decimal)
    MyBase.RaiseSalary(1.2D * Percent)
  End Sub
End Class
Public Class Archictect
    Inherits Programmer
    Public Sub New(ByVal theName As String, ByVal curSalary As Decimal)
        MyBase.New(theName, curSalary)
    End Sub
    Public Overloads Overrides Sub RaiseSalary(ByVal Percent As Decimal)
        MyBase.RaiseSalary(2D * Percent)
    End Sub
End Class