Create a comma-delimited list from an IEnumerable collection of Umbraco IPublishedContent Ids

Comma Delimited List from IPublishedContent IDs

 var storedVal = content.Aggregate<IPublishedContent, StringBuilder, string>(
                new StringBuilder()
                , (sb, x) => sb.Append(x.Id).Append((content.Last().Id==x.Id) ? "" : ",")
                , (sb) => sb.ToString()
                );