VB.Net Constructors

In VB.Net, a constructor is called whenever a class or struct is created. A constructor is a sub named New. You can overload the constructor simply by adding two or more New subs with various parameters (overloaded constructors).

If you do not create a constructor, VB.Net will create an implicit constructor that initializes all member fields to their default values.

Constructors can execute at two different times. Static constructors are executed by the CLR before any objects are instantiated. Regular constructors are executed when you create an object.

You can invoke the parent constructor with MyBase.New.

Working WinForms Example

The following example demonstrates using a constructor to initialize a public member field.

Create a form and place a button on it and alter the code as follows:

Public Class Form1

  Private Sub Button1_Click(ByVal sender As System.Object, _

      ByVal e As System.EventArgs) Handles Button1.Click
  

    Dim MyRobot As New Cyborg("Cameron")

    MessageBox.Show("My robot's name is " & MyRobot.CyborgName & ".")
  End Sub
End Class

  
Public Class Cyborg
  Public CyborgName As String

  Public Sub New(ByVal pName As String)
    CyborgName = pName
  End Sub
End Class

Overloading Constructors

Here is a working example of overloading a constructor. In this example, we overload our New() constructor so you can either pass in a name or set the name after creation.

Public Class Form1

  Private Sub Button1_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles Button1.Click

    Dim MyRobot1 As New Cyborg()
    MyRobot1.CyborgName = "John"
    MessageBox.Show("My robot's name is " & MyRobot1.CyborgName & ".")

    Dim MyRobot2 As New Cyborg("Cameron")
    MessageBox.Show("My robot's name is " & MyRobot2.CyborgName & ".")

  End Sub
End Class

 
Public Class Cyborg
  Public CyborgName As String

  Public Sub New()
  End Sub

  Public Sub New(ByVal pName As String)
    CyborgName = pName
  End Sub
End Class