private void buttonNewCategory_Click(object sender, EventArgs e)
        {
            var rssg = new RssCategory();

            var groupForm = new CategoryForm {
                RssCategory = rssg
            };

            if (groupForm.ShowDialog(this) == DialogResult.OK)
            {
                Settings.RssCategories.Add(rssg);
            }
        }
        private void buttonEditCategory_Click(object sender, EventArgs e)
        {
            var rssCategory = listBoxCategory.SelectedItem as RssCategory;

            if (rssCategory == null)
            {
                return;
            }

            var groupForm = new CategoryForm
            {
                RssCategory = rssCategory
            };

            groupForm.ShowDialog(this);

            groupsBindingSource.ResetBindings(false);
        }