private void BtnTraceSr_Click(object sender, RoutedEventArgs e)
        {
            lblTraceinfo.Content = btnTraceSr.Content;
            listTraceSr          = PanelTrace_db.PobierzTraceSr();

            grdTraceDane.Children.Clear();
            panelTraceSrednice = null;
            panelTraceSrednice = new PanelTraceSrednice(listTraceSr);

            grdTraceDane.Children.Add(panelTraceSrednice);
        }