private async Task <(string, DateTime, bool)> GenerateRss(string group) { var contents = await _contentsService.All() .Where(c => string.Equals(c.Group, group, StringComparison.OrdinalIgnoreCase)) .OrderByDescending(c => c.Created).Take(MaxRssItemCount).ToListAsync(); if (contents.Count == 0) { return(null, default, true);