Constructor Overriding in Visual Basic .NET

In this lesson, I will show you how to do constructor overriding in VB.NET. We have base class named People and we have sub class named Student

Both the classes have constructors Public Sub New(). Inside the constructor you can see console message

This is the People Class

Public Class People
    Private strFirstName As String
    Private strLastName As String
    Private dtrDateOfBirth As Date

    Public Sub New()
        Console.WriteLine("Super Class Constructor")
    End Sub
    Public Property FirstName() As String
        Get
            Return strFirstName
        End Get
        Set(value As String)
            strFirstName = value
        End Set
    End Property

    Public Property LastName() As String
        Get
            Return strLastName
        End Get
        Set(value As String)
            strLastName = value
        End Set
    End Property


    Public Property DateOfBirth() As String
        Get
            Return dtrDateOfBirth
        End Get
        Set(value As String)
            dtrDateOfBirth = value
        End Set
    End Property



End Class

This is the Student Class

Public Class Student
    Inherits People
    Private strCourse As String
    Public Sub New()

        Console.WriteLine("Sub Class Constructor")
    End Sub

  
    Public Property Course() As String
        Get
            Return strCourse
        End Get
        Set(value As String)
            strCourse = value
        End Set
    End Property


End Class

I have just created object p which is a instance of People and S instance of Student class

Module Module1

    Sub Main()

        Dim p As New People
        p.FirstName = "John"
        p.LastName = "Doe"
        p.DateOfBirth = Date.Parse("11-09-1980")

        Dim s As New Student
        Console.ReadLine()


    End Sub

End Module

You can see the console output as below

Super Class Constructor
Super Class Constructor
Sub Class Constructor

When you create a object from subclass. It first call the base class constructor and then call the sub class constructor

Now I am going to add another constructor with one argument to Sub Class

   Public Sub New(ByVal fName As String)
        Me.FirstName = fName
        Console.WriteLine("Sub Class Constructor with argument")
    End Sub

Now I will change the main module as below

Module Module1

    Sub Main()

        Dim p As New People
        p.FirstName = "John"
        p.LastName = "Doe"
        p.DateOfBirth = Date.Parse("11-09-1980")

        Dim s As New Student("John")
        Console.ReadLine()


    End Sub

End Module

Changed only the Line 10. It passes the constructor argument when creating the object

Now you get the output

Super Class Constructor
Super Class Constructor
Sub Class Constructor with argument