VB.Net/Class/Polymorphism

Demonstrate polymorphism in Point-Circle-Cylinder hierarchy

<source lang="vbnet"> 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

      </source>

PolyMorphism At Work

<source lang="vbnet"> 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

      </source>