Fix loading existing item on item details

Chapter06/Complete/MyMediaCollection/ViewModels/ItemDetailsViewModel.cs

@@ -41,12 +41,31 @@ namespace MyMediaCollection.ViewModels
             PopulateLists();
         }
 
-        public void InitializeItemDetailData(int itemId)
+        public async Task InitializeItemDetailDataAsync(int itemId)
         {
             _selectedItemId = itemId;
+            await PopulateExistingItemAsync(_dataService);
             IsDirty = false;
         }
 
+        private async Task PopulateExistingItemAsync(IDataService dataService)
+        {
+            if (_selectedItemId > 0)
+            {
+                var item = await _dataService.GetItemAsync(_selectedItemId);
+                Mediums.Clear();
+
+                foreach (string medium in dataService.GetMediums(item.MediaType).Select(m => m.Name))
+                    Mediums.Add(medium);
+
+                _itemId = item.Id;
+                ItemName = item.Name;
+                SelectedLocation = item.Location.ToString();
+                SelectedItemType = item.MediaType.ToString();
+                SelectedMedium = item.MediumInfo.Name;
+            }
+        }
+
         private void PopulateLists()
         {
             ItemTypes.Clear();

Chapter06/Complete/MyMediaCollection/Views/ItemDetailsPage.xaml.cs

@@ -34,7 +34,7 @@ namespace MyMediaCollection.Views
 
         public ItemDetailsViewModel ViewModel;
 
-        protected override void OnNavigatedTo(NavigationEventArgs e)
+        protected async override void OnNavigatedTo(NavigationEventArgs e)
         {
             base.OnNavigatedTo(e);
 
@@ -42,7 +42,7 @@ namespace MyMediaCollection.Views
 
             if (itemId > 0)
             {
-                ViewModel.InitializeItemDetailData(itemId);
+                await ViewModel.InitializeItemDetailDataAsync(itemId);
             }
         }
     }