private void Accept_Click(object sender, RoutedEventArgs e)
        {
            if ((designatorTextBox.Text != perItem.designator) |
                (nameTextBox.Text != perItem.name) |
                (quantityTextBox.Text != perItem.quantity) |
                (noteTextBox.Text != perItem.note) |
                ((bool)isNameUnderlinedCheckBox.IsChecked != perItem.isNameUnderlined))
            {
                perItem.designator       = designatorTextBox.Text;
                perItem.name             = nameTextBox.Text;
                perItem.quantity         = quantityTextBox.Text;
                perItem.note             = noteTextBox.Text;
                perItem.isNameUnderlined = (bool)isNameUnderlinedCheckBox.IsChecked;

                project.AddPerechenItem(perItem);

                this.DialogResult = true;
            }
        }