'Singleton模式
Public Class Singleton
    Private Shared uniqueInstance As New Singleton

    Private Sub New()

    End Sub

    Public Shared Function getInstance() As Singleton
        If uniqueInstance Is Nothing Then
            uniqueInstance = New Singleton
        End If
        Return uniqueInstance
    End Function

End Class

Public Class Singleton
    Private Shared _Singleton As Singleton = Nothing
    Private Shared _Mutex As New system.threading.Mutex '进程同步 

    Private Sub New()
        '类构造
    End Sub

    Public Shared Function Instance() As Singleton
        If _Singleton Is Nothing Then  'double-checked locking
            _Mutex.WaitOne()
            Try
                If _Singleton Is Nothing Then
                    _Singleton = New Singleton
                End If
            Finally
                _Mutex.ReleaseMutex()
            End Try
        End If
        Return _Singleton
    End Function
End Class