Public Class PrivateFieldNullTest

    Public Sub NullTestClass()
        _testClass = Nothing
    End Sub

    Private _testClass As TestClass
    Public Property GetTestClass() As TestClass
        Get
            If _testClass Is Nothing Then
                _testClass = New TestClass()
                _testClass.TestString = GetRandomString(5)
            End If

            Return _testClass
        End Get

        Set(value As TestClass)
            _testClass = value
        End Set
    End Property
End Class

Public Class TestClass
    Public Property TestString() As String
End Class

Private Sub NullTest()

    Dim toc As New PrivateFieldNullTest()

    Dim tc = toc.GetTestClass

    CheckIsSame.Text &= String.Format("NullTest - Before nullify '{0}';", tc.TestString)

    toc.NullTestClass()

    CheckIsSame.Text &= String.Format(" After nullify '{0}';", tc.TestString)
    CheckIsSame.Text &= String.Format(" new test string after Nullify '{0}';", toc.GetTestClass.TestString)
End Sub