Shared / Static Class in vb.net/C#

Shared / Static Class in vb.net/C#

VB.net     : Shared

C#            : Static

You can’t create object of Shared Class

Below Image show Properties and Method are not visible for Shared/Static Class

Public Class Form1

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

        'Module is VB.net are Shared Type Class.

        'Shared Class Example is ARC.Tools.GRIDManager

        'When Class s Defined as Shared There no need to create object of Class.

        'If you just want to create a class that you can't inherit, in C# you can use

        ' Sealed, and in VB.Net use NotInheritable.

        'The VB.Net equivalent of static is shared.

        'From the CLR point of view, C# static class is just "sealed" and "abstract" class.

        'You can 't create an instance, because it is abstract, and you can't inherit from it

        'since it is sealed. 'The rest is just some compiler magic.

        ' Shared Class Can't Have Interface or Inheritance POssible

        'You can't create object of Shared Or Static of Class. When No Method or Function is

        'Define without Shared KeyWord

        'Dim A As New Student

        'A.  ' This will not Show any Properties or Method from Shared class

       

        Student.Name = "Swtin"

        Student.Age = 16

        Student.DoSomething()

        Student.GetSomething(132123132)

        'This will Overwrite Earlier Value

        Student.Name = "ABC"

        Student.Age = 20

        Student.DoSomething()

        'Allow to create Multiple Objects but all Object will Retuen Same Value.

        School.Schoolname = "SARC"

        'Object of Class is Allowed as Does't have Private Constructor and it has non Shared Function

        'Dim S As New School

        'S.name = "ARC" ' This will Throws Exceptation as Shared Type of Proeprty and Method are not visble in Object

        ' Object Of Class will not Return Shared Methods,Function AND Properties

        Dim X As New School

        Console.WriteLine(X.getSchoolname())

        Dim X2 As New School

        Console.WriteLine(X2.getSchoolname())

 'All Object of Scholl Class will return Same Value which is assigned to Shared Variable

    End Sub

    Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click

        Dim X As New School

        Console.WriteLine(X.getSchoolname())

'Even this will Return Same value as above. It will Across Module/Class/Forms

    End Sub

    Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click

        'SingleTone Sample

        ClassRooms.ClassRoomForStd = 10

        ClassRooms.ClassRoomForDiv = "A"

        'The private constructor simply prevents client code creating an instance (which isn't needed for

       ' anything).

        'Dim C As New ClassRooms 'This will Throw Error As PRIVATE constructor Defined in Class

        Dim C As ClassRooms

        C = ClassRooms.GetInstance

        C.DoSomething() 'Both method will Return Same Value. As its Point to same Instance

        Dim D As ClassRooms

        D = ClassRooms.GetInstance

        D.DoSomething()  'Both method will Return Same Value. As its Point to same Instance

    End Sub

End Class

Public Interface ITest

    Sub DoSomething()

End Interface

'// Shared/Static  Class

Public NotInheritable Class Student

    'Implements ITest  ' Shared Class Can't Have Interface or Inheritance POssible

    Public Shared Property Name As String

    Public Shared Property Age As Integer

    'This will Throw Error

    'Public Shared Sub DoSomething() Implements ITest.DoSomething

    Public Shared Sub DoSomething()

        Console.WriteLine("Name :- " & Name & " - Age " + Age.ToString)

    End Sub

    Public Shared Function GetSomething(Value) As String

        Console.WriteLine(Value)

        Return "Get Something"

    End Function

    'IF this Defined the Object of this Class will be Allowed

    'Public Sub Test()

    '    ''

    'End Sub

End Class

'// Shared/Static  Class

Public Class School

    Public Shared Schoolname As String

    Public Function getSchoolname() As String

        Return Schoolname

    End Function

End Class

'// Singleton Class

Public Class ClassRooms

    Implements ITest ' Singleton Class will Allow to have Inherits and Implementation

    'Singelton provides you the facility to implement the interfaces

    'Singelton pattren has wide usage specialy where you have to limit your application to create only one instance

    'just like in many games you have only one instance

    Private Shared ClassRm As ClassRooms

    Public Shared Property ClassRoomForStd() As Integer

    Public Shared Property ClassRoomForDiv() As String

    'When Private Construtor is Defined. Object of Class Can't have New while Defining.

    Private Sub New()

        'This Done to not allow User to Create Instance of Class.

    End Sub

    'This is Singleton Implemention where Object of Static or Shared Class Are created inside and returned using object

    Public Shared Function GetInstance() As ClassRooms

        If IsNothing(ClassRm) = True Then

            ClassRm = New ClassRooms

        End If

        Return ClassRm

    End Function

    'Implemented Method

    Public Sub DoSomething() Implements ITest.DoSomething

        Console.WriteLine("Interface Implemented Method")

        Console.WriteLine(ClassRoomForStd.ToString & "- " & ClassRoomForDiv.ToString)

    End Sub

End Class

Singleton object stores in Heap but, static object stores in stack

We can clone the object of Singleton but, we can not clone the static class object

Singleton class follow the OOP(object oriented principles) but not static class

we can implement interface with Singleton class but not with Static class.

Static Class:-

You cannot create the instance of static class.

Loaded automatically by the .NET Framework common language runtime (CLR) when the program or namespace containing the class is loaded.

Static Class cannot have constructor.

We cannot pass the static class to method.

We cannot inherit Static class to another Static class in C#.

A class having all static methods.

Better performance (static methods are bonded on compile time)

Singleton:-

You can create one instance of the object and reuse it.

Singleton instance is created for the first time when the user requested.

Singleton class can have constructor.

You can create the object of singleton class and pass it to method.

Singleton class does not say any restriction of Inheritance.

We can dispose the objects of a singleton class but not of static class.

Methods can be overridden.

Can be lazy loaded when need (static classes are always loaded).

We can implement interface(static class can not implement interface).