private void GotFocusReset(object sender, RoutedEventArgs e) { TextBox textBox = sender as TextBox; FirstIP.ClearValue(Label.ContentProperty); LastIP.ClearValue(Label.ContentProperty); SubnetMask.ClearValue(Label.ContentProperty); nHosts.ClearValue(Label.ContentProperty); textBox.GotFocus -= GotFocusReset; }