Constructor in VB.NET

In this article we will describe the Constructor.
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Constructor:-A Constructor is a special  kinds of member function that used to initialize the object .
A constructor is like  a method in that it contain executable code and may be defined with parameter.
this is first method that is run when an instance of type is created.
constructor is two types in VB.NET

  • Instance constructor
  • Shared constructor

Instance constructor:-"An Instance constructor runs whenever the CLR creates an object from a class" 

coding for instance constructor:-

Module Module1
    Sub Main()
        Dim con As New Constructor("Hello world")
        Console.WriteLine(con.display())
        'display method
    End Sub
End
Module
Public
Class Constructor
    Public x As String
    Public Sub New(ByVal value As String)
        'constructor
        x = value
        'storing the value of x in constructor
    End Sub
    Public Function display() As String
        Return x
        'returning the stored value
    End Function

End
Class

Output:- Hellow world

Shared Constructor:-
"Shared constructor  are most often  used to initialize class level data such as shared fields"

coding for shared constructor
:-

Module Testcons
    Sub Main()
        Console.WriteLine("100")
        B.G()
        Console.WriteLine("200")
    End Sub

End
Module 

Class A
    Shared Sub New()
        Console.WriteLine("Init A")
    End Sub
End Class
Class B
    Inherits A
    Shared Sub New()
        Console.WriteLine("Init B")
    End Sub
    Public Shared Sub G()
        Console.WriteLine("Hello world")
    End Sub
End
Class


Output:
100
              200
              Hello world

Note:
Some important points for shared constructor
  •  Shared constructors are run before any instance of a class type is created.
     
  •  Shared constructors are run before any instance members of a structure type are accessed, or before any
      constructor of a structure type is explicitly called. Calling the implicit parameter less constructor created for
      structures will not cause the shared constructor to run.
     
  •   Shared constructors are run before any of the type's shared members are referenced.
     
  •   Shared constructors are run before any types that derive from the type are loaded.
     
  •   A shared constructor will not be run more than once during a single execution of a program.
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