private async void mainpivot_SelectionChanged(object sender, SelectionChangedEventArgs e) { string tid = (mainpivot.SelectedItem as PivotItem).Tag.ToString(); GridView gridview = FindName("list" + tid) as GridView; if (gridview != null && gridview.Items.Count == 0) { gridview.ItemsSource = await ContentServ.GetRankItemsAsync(tid); } }