private void BtDeleteVisit_Click(object sender, RoutedEventArgs e)
        {
            Visit v1 = (Visit)visitDataGrid.SelectedItem;

            if (v1 != null)
            {
                MessageBoxResult result = System.Windows.MessageBox.Show("Czy usunąć wizytę dla pacjenta " + v1.Referral.Patient.Name + " " + v1.Referral.Patient.Surname + " z dnia " + v1.VisitDate.ToShortDateString() + "?", "Usuwanie pacjenta", MessageBoxButton.YesNo);
                if (result == MessageBoxResult.Yes)
                {
                    Visit.DeleteVisit(v1, dbcontext);
                }
            }
            physiotherapistDataGrid.Items.Refresh();
        }