Fix: Fixed possible NullReferenceException with DispatcherQueue.EnqueueAsync()

src/Files.App/App.xaml.cs

@@ -270,7 +270,7 @@ public void OnActivated(AppActivationArguments activatedEventArgs)
 			var data = activatedEventArgs.Data;
 
 			// InitializeApplication accesses UI, needs to be called on UI thread
-			_ = Window.DispatcherQueue.EnqueueAsync(() => Window.InitializeApplication(data));
+			_ = Window.DispatcherQueue.EnqueueOrInvokeAsync(() => Window.InitializeApplication(data));
 		}
 
 		/// <summary>
@@ -475,7 +475,7 @@ private static void AppUnhandledException(Exception ex, bool shouldShowNotificat
 				userSettingsService.AppSettingsService.RestoreTabsOnStartup = true;
 				userSettingsService.GeneralSettingsService.LastCrashedTabList = lastSessionTabList;
 
-				Window.DispatcherQueue.EnqueueAsync(async () =>
+				Window.DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 				{
 					await Launcher.LaunchUriAsync(new Uri("files-uwp:"));
 				}).Wait(1000);

src/Files.App/BaseLayout.cs

@@ -257,7 +257,7 @@ internal set
 						if (selectedItems.Count == 1)
 						{
 							SelectedItemsPropertiesViewModel.SelectedItemsCountString = $"{selectedItems.Count} {"ItemSelected/Text".GetLocalizedResource()}";
-							DispatcherQueue.EnqueueAsync(async () =>
+							DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 							{
 								// Tapped event must be executed first
 								await Task.Delay(50);
@@ -1355,7 +1355,7 @@ protected async void ValidateItemNameInputText(TextBox textBox, TextBoxBeforeTex
 			{
 				args.Cancel = true;
 
-				await DispatcherQueue.EnqueueAsync(() =>
+				await DispatcherQueue.EnqueueOrInvokeAsync(() =>
 				{
 					var oldSelection = textBox.SelectionStart + textBox.SelectionLength;
 					var oldText = textBox.Text;

src/Files.App/DataModels/NavigationControlItems/DriveItem.cs

@@ -184,7 +184,7 @@ public static async Task<DriveItem> CreateFromPropertiesAsync(StorageFolder root
 			item.DeviceID = deviceId;
 			item.Root = root;
 
-			_ = App.Window.DispatcherQueue.EnqueueAsync(() => item.UpdatePropertiesAsync());
+			_ = App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => item.UpdatePropertiesAsync());
 
 			return item;
 		}

src/Files.App/DataModels/NavigationControlItems/LocationItem.cs

@@ -95,7 +95,7 @@ public ulong SpaceUsed
 			{
 				SetProperty(ref spaceUsed, value);
 
-				App.Window.DispatcherQueue.EnqueueAsync(() => OnPropertyChanged(nameof(ToolTipText)));
+				App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => OnPropertyChanged(nameof(ToolTipText)));
 			}
 		}
 

src/Files.App/DataModels/SidebarPinnedModel.cs

@@ -115,20 +115,20 @@ public async Task<LocationItem> CreateLocationItemFromPathAsync(string path)
 				{
 					var iconData = await FileThumbnailHelper.LoadIconFromStorageItemAsync(res.Result, 96u, ThumbnailMode.ListView);
 					locationItem.IconData = iconData;
-					locationItem.Icon = await App.Window.DispatcherQueue.EnqueueAsync(() => locationItem.IconData.ToBitmapAsync());
+					locationItem.Icon = await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => locationItem.IconData.ToBitmapAsync());
 				}
 
 				if (locationItem.IconData is null)
 				{
 					locationItem.IconData = await FileThumbnailHelper.LoadIconWithoutOverlayAsync(path, 96u);
 
 					if (locationItem.IconData is not null)
-						locationItem.Icon = await App.Window.DispatcherQueue.EnqueueAsync(() => locationItem.IconData.ToBitmapAsync());
+						locationItem.Icon = await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => locationItem.IconData.ToBitmapAsync());
 				}
 			}
 			else
 			{
-				locationItem.Icon = await App.Window.DispatcherQueue.EnqueueAsync(() => UIHelpers.GetSidebarIconResource(Constants.ImageRes.Folder));
+				locationItem.Icon = await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => UIHelpers.GetSidebarIconResource(Constants.ImageRes.Folder));
 				locationItem.IsInvalid = true;
 				Debug.WriteLine($"Pinned item was invalid {res.ErrorCode}, item: {path}");
 			}

src/Files.App/Extensions/DispatcherQueueExtensions.cs

@@ -0,0 +1,48 @@
+using CommunityToolkit.WinUI;
+using Microsoft.UI.Dispatching;
+using System;
+using System.Threading.Tasks;
+
+namespace Files.App.Extensions
+{
+	// Window.DispatcherQueue seems to be null sometimes.
+	// We don't know why, but as a workaround, we invoke the function directly if DispatcherQueue is null.
+	public static class DispatcherQueueExtensions
+	{
+		public static Task EnqueueOrInvokeAsync(this DispatcherQueue? dispatcher, Func<Task> function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
+		{
+			if (dispatcher is not null)
+				return dispatcher.EnqueueAsync(function, priority);
+			else
+				return function();
+		}
+
+		public static Task<T> EnqueueOrInvokeAsync<T>(this DispatcherQueue? dispatcher, Func<Task<T>> function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
+		{
+			if (dispatcher is not null)
+				return dispatcher.EnqueueAsync(function, priority);
+			else
+				return function();
+		}
+
+		public static Task EnqueueOrInvokeAsync(this DispatcherQueue? dispatcher, Action function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
+		{
+			if (dispatcher is not null)
+				return dispatcher.EnqueueAsync(function, priority);
+			else
+			{
+				function();
+				return Task.CompletedTask;
+			}
+		}
+
+		public static Task<T> EnqueueOrInvokeAsync<T>(this DispatcherQueue? dispatcher, Func<T> function, DispatcherQueuePriority priority = DispatcherQueuePriority.Normal)
+		{
+			if (dispatcher is not null)
+				return dispatcher.EnqueueAsync(function, priority);
+			else
+				return Task.FromResult(function());
+		}
+
+	}
+}

src/Files.App/Filesystem/Cloud/CloudDrivesManager.cs

@@ -1,6 +1,7 @@
 using CommunityToolkit.Mvvm.DependencyInjection;
 using CommunityToolkit.WinUI;
 using Files.App.DataModels.NavigationControlItems;
+using Files.App.Extensions;
 using Files.App.Helpers;
 using Files.Shared;
 using Files.Shared.Cloud;
@@ -53,7 +54,7 @@ public async Task UpdateDrivesAsync()
 				try
 				{
 					cloudProviderItem.Root = await StorageFolder.GetFolderFromPathAsync(cloudProviderItem.Path);
-					_ = App.Window.DispatcherQueue.EnqueueAsync(() => cloudProviderItem.UpdatePropertiesAsync());
+					_ = App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => cloudProviderItem.UpdatePropertiesAsync());
 				}
 				catch (Exception ex)
 				{
@@ -72,7 +73,7 @@ public async Task UpdateDrivesAsync()
 				{
 					cloudProviderItem.IconData = iconData;
 					await App.Window.DispatcherQueue
-						.EnqueueAsync(async () => cloudProviderItem.Icon = await iconData.ToBitmapAsync());
+						.EnqueueOrInvokeAsync(async () => cloudProviderItem.Icon = await iconData.ToBitmapAsync());
 				}
 
 				lock (drives)

src/Files.App/Filesystem/Search/FolderSearch.cs

@@ -393,7 +393,7 @@ private ListedItem GetListedItemAsync(string itemPath, WIN32_FIND_DATA findData)
 					{
 						if (t.IsCompletedSuccessfully && t.Result is not null)
 						{
-							_ = FilesystemTasks.Wrap(() => App.Window.DispatcherQueue.EnqueueAsync(async () =>
+							_ = FilesystemTasks.Wrap(() => App.Window.DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 							{
 								listedItem.FileImage = await t.Result.ToBitmapAsync();
 							}, Microsoft.UI.Dispatching.DispatcherQueuePriority.Low));

src/Files.App/Helpers/DynamicDialogFactory.cs

@@ -98,7 +98,7 @@ public static DynamicDialog GetFor_RenameDialog()
 			inputText.Loaded += (s, e) =>
 			{
 				// dispatching to the ui thread fixes an issue where the primary dialog button would steal focus
-				_ = inputText.DispatcherQueue.EnqueueAsync(() => inputText.Focus(FocusState.Programmatic));
+				_ = inputText.DispatcherQueue.EnqueueOrInvokeAsync(() => inputText.Focus(FocusState.Programmatic));
 			};
 
 			dialog = new DynamicDialog(new DynamicDialogViewModel()

src/Files.App/Helpers/MenuFlyoutHelper.cs

@@ -1,4 +1,5 @@
 using CommunityToolkit.WinUI;
+using Files.App.Extensions;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
 using System;
@@ -101,7 +102,7 @@ private static async void SetupItems(MenuFlyout menu)
 				return;
 			}
 
-			await menu.DispatcherQueue.EnqueueAsync(() =>
+			await menu.DispatcherQueue.EnqueueOrInvokeAsync(() =>
 			{
 				menu.Items.Clear();
 				AddItems(menu.Items, itemSource);

src/Files.App/Helpers/ThemeHelper.cs

@@ -75,7 +75,7 @@ private static async void UiSettings_ColorValuesChanged(UISettings sender, objec
 				titleBar = App.GetAppWindow(currentApplicationWindow)?.TitleBar;
 
 			// Dispatch on UI thread so that we have a current appbar to access and change
-			await currentApplicationWindow.DispatcherQueue.EnqueueAsync(ApplyTheme);
+			await currentApplicationWindow.DispatcherQueue.EnqueueOrInvokeAsync(ApplyTheme);
 		}
 
 		private static void ApplyTheme()

src/Files.App/Interacts/BaseLayoutCommandImplementationModel.cs

@@ -100,7 +100,7 @@ public virtual async void OpenDirectoryInNewTab(RoutedEventArgs e)
 		{
 			foreach (ListedItem listedItem in SlimContentPage.SelectedItems)
 			{
-				await App.Window.DispatcherQueue.EnqueueAsync(async () =>
+				await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 				{
 					await mainPageViewModel.AddNewTabByPathAsync(typeof(PaneHolderPage), (listedItem as ShortcutItem)?.TargetPath ?? listedItem.ItemPath);
 				},

src/Files.App/ServicesImplementation/RemovableDrivesService.cs

@@ -1,5 +1,6 @@
 using CommunityToolkit.WinUI;
 using Files.App.DataModels.NavigationControlItems;
+using Files.App.Extensions;
 using Files.App.Filesystem;
 using Files.App.Helpers;
 using Files.App.Storage.WindowsStorage;
@@ -66,7 +67,7 @@ public async Task UpdateDrivePropertiesAsync(ILocatableFolder drive)
 			var rootModified = await FilesystemTasks.Wrap(() => StorageFolder.GetFolderFromPathAsync(drive.Path).AsTask());
 			if (rootModified && drive is DriveItem matchingDriveEjected)
 			{
-				_ = App.Window.DispatcherQueue.EnqueueAsync(() =>
+				_ = App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() =>
 				{
 					matchingDriveEjected.Root = rootModified.Result;
 					matchingDriveEjected.Text = rootModified.Result.DisplayName;

src/Files.App/ServicesImplementation/ThreadingService.cs

@@ -1,4 +1,5 @@
 using CommunityToolkit.WinUI;
+using Files.App.Extensions;
 using Files.Backend.Services;
 using Microsoft.UI.Dispatching;
 using System;
@@ -17,12 +18,12 @@ public ThreadingService()
 
 		public Task ExecuteOnUiThreadAsync(Action action)
 		{
-			return _dispatcherQueue.EnqueueAsync(action);
+			return _dispatcherQueue.EnqueueOrInvokeAsync(action);
 		}
 
 		public Task<TResult?> ExecuteOnUiThreadAsync<TResult>(Func<TResult?> func)
 		{
-			return _dispatcherQueue.EnqueueAsync<TResult?>(func);
+			return _dispatcherQueue.EnqueueOrInvokeAsync<TResult?>(func);
 		}
 	}
 }

src/Files.App/UserControls/Widgets/DrivesWidget.xaml.cs

@@ -61,7 +61,7 @@ public async Task LoadCardThumbnailAsync()
 
 			// Thumbnail data is valid, set the item icon
 			if (thumbnailData is not null && thumbnailData.Length > 0)
-				Thumbnail = await thumbnailData.ToBitmapAsync(Constants.Widgets.WidgetIconSize);
+				Thumbnail = await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => thumbnailData.ToBitmapAsync(Constants.Widgets.WidgetIconSize));
 		}
 
 		public int CompareTo(DriveCardItem? other) => Item.Path.CompareTo(other?.Item?.Path);
@@ -146,7 +146,7 @@ public DrivesWidget()
 
 		private async void Drives_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
 		{
-			await DispatcherQueue.EnqueueAsync(async () =>
+			await DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 			{
 				foreach (DriveItem drive in drivesViewModel.Drives.ToList())
 				{

src/Files.App/UserControls/Widgets/QuickAccessWidget.xaml.cs

@@ -97,7 +97,7 @@ public async Task LoadCardThumbnailAsync()
 			}
 			if (thumbnailData is not null && thumbnailData.Length > 0)
 			{
-				Thumbnail = await thumbnailData.ToBitmapAsync(Constants.Widgets.WidgetIconSize);
+				Thumbnail = await App.Window.DispatcherQueue.EnqueueOrInvokeAsync(() => thumbnailData.ToBitmapAsync(Constants.Widgets.WidgetIconSize));
 			}
 		}
 	}
@@ -247,7 +247,7 @@ private async void ModifyItem(object? sender, ModifyQuickAccessEventArgs? e)
 			if (e is null)
 				return;
 
-			await DispatcherQueue.EnqueueAsync(async () =>
+			await DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 			{
 				if (e.Reset)
 				{

src/Files.App/UserControls/Widgets/RecentFilesWidget.xaml.cs

@@ -210,7 +210,7 @@ public async Task RefreshWidget()
 
 		private async void Manager_RecentFilesChanged(object sender, NotifyCollectionChangedEventArgs e)
 		{
-			await DispatcherQueue.EnqueueAsync(async () =>
+			await DispatcherQueue.EnqueueOrInvokeAsync(async () =>
 			{
 				// e.Action can only be Reset right now; naively refresh everything for simplicity
 				await UpdateRecentsList(e);