public Group[] GetGroups(Action <Group[]> calback) { var entity = CreateEntity(); _rest.ExchangeAsync <GetGroupsResponce>("/api/v1/groups.json", HttpMethod.GET, entity, r => { if (r.Error == null) { calback(r.Response.Body.items.Select(x => x.group).ToArray()); } else { throw new Exception("get groups failed", r.Error); } }); return(null); }