'''
''' Singleton generic thread safe
'''
'''
''' Codebase by A.Cavallaro
Public Class Singleton(Of T As {Class, New})
Private Shared ReadOnly l_ThreadSafeIstance As New T

'''
''' Nessun costruttore per singleton
'''
'''
Private Sub New()
End Sub
End Class


”’
”’ Singleton generic thread safe
”’
”’
”’ Codebase by A.Cavallaro
Public Class Singleton(Of T As {Class, New})
Private Shared ReadOnly l_ThreadSafeIstance As New T

”’
”’ Ritorna l’istanza thread-safe del singleton
”’
”’
”’
Public Shared Function GetInstance() As T
Return l_ThreadSafeIstance
End Function

”’
”’ Nessun costruttore per singleton
”’
”’
Private Sub New()
End Sub
End Class

Threading certainly does throw a whole new wrinkle on things. The article you linked to is very informative and helpful.

To implement the second version, simple thread-safety, mentioned in the linked article, my code example should look like this, if I followed it correctly:

Public Class MySingleton

    Private Shared _thisInstance As MySingleton
    Private Shared PadLock As New Object

    Protected Sub New()
        'initialization code goes here
    End Sub

    Public Shared Function GetSingleton() As MySingleton
        '
        ' Prevents multiple threads from creating
        ' separate instances
        '
        SyncLock PadLock
            '
            ' initialize object if it hasn't already been done
            '
            If _thisInstance Is Nothing Then
                _thisInstance = New MySingleton
            End If
            '
            ' return the initialized instance
            '
            Return _thisInstance
        End SyncLock
    End Function

End Class

James’ code would be the fifth version, fully lazy instantiation, is that correct?

Thanks again for everyone’s input.

example in c#
http://www.yoda.arachsys.com/csharp/singleton.html


Public Module MySingleton

End Module


Yes. That would work for creating a generic Singleton object. The only limitation is that you can only use objects that have a Public New that takes no parameters. String would be an example of an object that would not work although you could wrapper it in another class easily enough if you wanted.

The interesting thing about this code example is that you can use this Singleton provider to create a Singleton version of a class without having to have the code in the class itself.

Thanks again for a great example.

Public Class Singleton(Of T As {Class, New})
	Public Shared ReadOnly Property Instance() As T
		Get
			Return SingletonCreator._instance
		End Get
	End Property

	Class SingletonCreator
		Shared Sub New()
		End Sub

		Friend Shared ReadOnly _instance As New T()
	End Class
End Class