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Working of Constructors in vb.net
19 October, 2020
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Constructors:
It is used to initialize the members of the class VB.Net supports two types of constructors
- Instance constructors
- Shared constructors
A) Instance Constructors:
It is used to initialize the instance and the shared members of the class
Syntax:
[Modifier] sub new ([arg info])
statement(s)
- - - - - - -
- - - - - -
End sub
Note:
- Instance constructors will be invoked every time a new object is created for the class.
- A class can have any number of instance constructors.
- If a class is defined with more than one constructor then it is said to be the classes overloaded with constructors.
- If a constructor is defined using arguments then it is said to be a parameterized constructor
- If a constructor is defined without any arguments then it is said to the zero-argument constructor.
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B) Shared Constructors:
It is used to initialize the shared members of the class.
Syntax:
Shared sub new ( )
statement(s)
- - - - - -
- - - - - -
End sub
Observation:
- Shared constructors will be invoked only once whenever the class definition is loaded.
- A class can have a maximum of only one shared constructor.
- Shared constructors can’t accept any arguments.
Project [menu] à Add new item à Module
Name: Constructors ‘‘Demo
‘‘‘Demo on constructors . . . . .
Imports system
Module constructors ‘‘Demo
Class Test
Public i as integer
Public shared s as an integer
Sub new( ) ‘Instance constructor’
P = 100
S = 1000
End sub
Shared sub new( ) ‘Shared constructor’
S = 500
P = 500 error
End sub
End class
Sub main ( )
Console.WriteLine (“value of s before object creation: {0}”, Test.s)
Dim t As new Test
Console.WriteLine (“Value of t and s” after object creation: {0}, {1}”, t.p, Test.s)
End sub
End module
Observation:
- Whenever the value for the shared members has to be initialized before creating an object or if a constant value has to be assigned for the shared member then shared constructors should be used to initialize the shared members.
- Whenever the value for the shared member has to be reinitialized with a new value for every new instance created for a class then the instance constructor should be used to initialize the shared members.