private async Task UpdateCalendar(ResourceCalendar calendar)
        {
            Cache.ClearAll();

            DjangoCalendar dc = await GetDjangoCalendar(calendar);

            foreach (var newEntry in ParseEntries(calendar))
            {
                var old = dc.Results.FirstOrDefault(row => row.Start == newEntry.Start && row.End == newEntry.End);
                if (old != null)
                {
                    old.Used = true;
                }
                else
                {
                    dc.Results.Add(newEntry);
                }
            }
            foreach (var entry in dc.Results)
            {
                if (entry.ID != null && entry.Used)
                {
                    continue;
                }
                if (entry.ID != null)
                {
                    await DeleteItem(entry.ID);
                }
                else
                {
                    await PostJson("calendarentries/", Serialize(entry));
                }
            }
        }
        private async Task FillResourceCalendar(ResourceCalendar calendar)
        {
            DjangoCalendar dc = await GetDjangoCalendar(calendar);

            foreach (var reserved in dc.Results)
            {
                reserved.Start = reserved.Start;
                reserved.End   = reserved.End;
                FillReserved(reserved, calendar);
            }
        }