dim PersonList as New ObservableCollection(Of Person)
 
Private Sub AddPerson_Click(ByVal sender As System.Object, ByVal e As _
  System.Windows.RoutedEventArgs)
 
  PersonList.Add(New Person() With {.FirstName = "Vorname", .LastName = _
    "Nachname", .Age = "23", .StartDate = New DateTime(2007, 8, 1), _
    .IsFullEmployee = False})
 
End Sub

  Public Sub AddPersonFromPopUp(ByVal strFirstName As String, ByVal strLastName _
    As String, ByVal intAge As Integer, ByVal bolIsFullEmployee As Boolean)
 
    PersonList.Add(New Person() With {.FirstName = strFirstName, .LastName = _
      strLastName, .Age = intAge, .IsFullEmployee = bolIsFullEmployee})
 
 End Sub

Dim MainPage as New Page()
MainPage.AddPersonFromPopup(...)