fix possible call from invalid thread error

Author: hendrikmennen

src/OneWare.PackageManager/ViewModels/PackageManagerViewModel.cs

@@ -3,6 +3,7 @@
 using System.Reactive.Linq;
 using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Threading;
 using CommunityToolkit.Mvvm.Input;
 using DynamicData.Binding;
 using Microsoft.Extensions.Logging;
@@ -56,14 +57,19 @@ public PackageManagerViewModel(IPackageService packageService, IHttpService http
 
         SelectedCategory = GetAllCategory() ?? PackageCategories.FirstOrDefault();
 
-        _packageService.WhenValueChanged(x => x.IsUpdating).Subscribe(x => { IsLoading = x; });
+        _packageService.WhenValueChanged(x => x.IsUpdating)
+            .Subscribe(x => Dispatcher.UIThread.Post(() => IsLoading = x));
 
         UpdateAllCommand = new AsyncRelayCommand(UpdateAllAsync, () => _packageService.Packages.Any(x => x.Value.Status == PackageStatus.UpdateAvailable));
 
         Observable.FromEventPattern(_packageService, nameof(_packageService.PackagesUpdated)).Subscribe(_ =>
         {
-            ConstructPackageViewModels();
-            UpdateAllCommand.NotifyCanExecuteChanged();
+            // PackagesUpdated can be raised from a background thread
+            Dispatcher.UIThread.Post(() =>
+            {
+                ConstructPackageViewModels();
+                UpdateAllCommand.NotifyCanExecuteChanged();
+            });
         });
 
         ConstructPackageViewModels();