private void buttonEditRSS_Click(object sender, EventArgs e)
        {
            var rssWebsite = listBoxRSS.SelectedItem as RssWebsite;

            if (rssWebsite == null)
            {
                return;
            }

            var subgroupForm = new RSSForm
            {
                RssWebsite = rssWebsite
            };

            subgroupForm.ShowDialog(this);

            subgroupsBindingSource.ResetBindings(false);
        }
        private void buttonNewRSS_Click(object sender, EventArgs e)
        {
            var rssCategory = listBoxCategory.SelectedItem as RssCategory;

            if (rssCategory == null)
            {
                return;
            }

            var rssWebsite = new RssWebsite();

            var subgroupForm = new RSSForm
            {
                RssWebsite = rssWebsite
            };

            if (subgroupForm.ShowDialog(this) == DialogResult.OK)
            {
                rssCategory.RssWebsites.Add(rssWebsite);
            }
        }