/// <summary>
        /// write changes to database (insert or update)
        /// </summary>
        private void btnSave_Click(object sender, RoutedEventArgs e)
        {
            //assign form data to _dir object
            _dir.name        = txtDirName.Text;
            _dir.description = txtDirDescr.Text;
            _dir.color       = (cmbLabel.SelectedIndex > -1)
                ? ((ComboBoxItem)cmbLabel.SelectedItem).Background.ToString()
                : "";

            //edit data
            if (DirectoryController.InsertUpdate(_dir) > 0)
            {
                MessageBox.Show("Directory sucessfully edited", "", MessageBoxButton.OK, MessageBoxImage.Information);
                this.DialogResult = true;
            }
        }