fix sort issue

Billing.Shared/Views/BillPage.xaml.cs

@@ -60,7 +60,7 @@ namespace Billing.Views
                     b.CreateTime.Year == e.Date.Year &&
                     b.CreateTime.Month == e.Date.Month &&
                     b.CreateTime.Day == e.Date.Day);
-                Bills = new List<UIBill>(bills.Select(b => WrapBill(b)));
+                Bills = new List<UIBill>(bills.OrderBy(b => b.CreateTime).Select(b => WrapBill(b)));
                 RefreshBalance(Bills);
                 MainThread.BeginInvokeOnMainThread(async () => await scrollView.ScrollToAsync(0, 0, true));
             });