private void DeleteButton_Click(object sender, RoutedEventArgs e)
        {
            Tag tag = (Tag)dataGridtag.SelectedItem;

            TagDataService tagDataService = new TagDataService(new EntityFramework.TimetableManagerDbContext());

            tagDataService.DeleteTag(tag.TagId).ContinueWith(result =>
            {
                MessageBox.Show("Deleted");
            });

            _ = TagDataList.Remove(tag);
        }