public async System.Threading.Tasks.Task <ICollection <HistoryData> > GetAllHistoryAsync(string username)
        {
            ICollection <IHistory> histories = await marketUsers.GetAllHistory(username);

            ICollection <HistoryData> ret = new HashSet <HistoryData>();

            foreach (IHistory his in histories)
            {
                ret.Add(new HistoryData(his));
            }
            return(ret);
        }