private async Task QueryTrending(DiscoverItem item) { CommonProvider common = new CommonProvider(); List <TrendingResult> result = new List <TrendingResult>(); if (pageIndex == 0) { if (TrendingList == null) { TrendingList = new ObservableCollection <TrendingResult>(); } else { TrendingList.Clear(); } } if (TypeSelectedItem.HotType != HotTopicType.None) { result = await common.QueryDiscover(TypeSelectedItem.HotType, pageIndex + 1, 20, new List <TrendingResult>(TrendingList)); } if (TypeSelectedItem.Type != TopicType.None) { int index = 0; if (TrendingList.Count != 0) { index = TrendingList[TrendingList.Count - 1].RecommendedAt - 1; } result = await common.QueryDiscover(TypeSelectedItem.Type, index, 20, 20); } result.ForEach(x => TrendingList.Add(x)); pageIndex++; }