c#如何把List變成json

  List<titles> t = v.getData_titles(page-1,rows,id);

        DataContractJsonSerializer json = new DataContractJsonSerializer(t.GetType());
        string szJson = "";
        //序列化
        using (MemoryStream stream = new MemoryStream())
        {
            json.WriteObject(stream, t);
            szJson = Encoding.UTF8.GetString(stream.ToArray());

        }