Code Quality: Fixed null warnings in MainPage.xaml.cs

src/Files.App/Helpers/Navigation/NavigationHelpers.cs

@@ -211,7 +211,7 @@ private static async Task UpdateTabInfoAsync(TabBarItem tabItem, object navigati
 			return (tabLocationHeader, iconSource, toolTipText);
 		}
 
-		public static async Task UpdateInstancePropertiesAsync(object navigationArg)
+		public static async Task UpdateInstancePropertiesAsync(object? navigationArg)
 		{
 			await SafetyExtensions.IgnoreExceptions(async () =>
 			{

src/Files.App/UserControls/AddressToolbar.xaml.cs

@@ -46,7 +46,7 @@ public bool ShowSearchBox
 		// Using a DependencyProperty as the backing store for ViewModel.  This enables animation, styling, binding, etc...
 		public static readonly DependencyProperty ViewModelProperty =
 			DependencyProperty.Register(nameof(ViewModel), typeof(ToolbarViewModel), typeof(AddressToolbar), new PropertyMetadata(null));
-		public ToolbarViewModel ViewModel
+		public ToolbarViewModel? ViewModel
 		{
 			get => (ToolbarViewModel)GetValue(ViewModelProperty);
 			set => SetValue(ViewModelProperty, value);

src/Files.App/UserControls/InnerNavigationToolbar.xaml.cs

@@ -27,7 +27,7 @@ public InnerNavigationToolbar()
 
 		public AppModel AppModel => App.AppModel;
 
-		public ToolbarViewModel ViewModel
+		public ToolbarViewModel? ViewModel
 		{
 			get => (ToolbarViewModel)GetValue(ViewModelProperty);
 			set => SetValue(ViewModelProperty, value);

src/Files.App/UserControls/StatusBarControl.xaml.cs

@@ -21,7 +21,7 @@ public DirectoryPropertiesViewModel? DirectoryPropertiesViewModel
 		public static readonly DependencyProperty DirectoryPropertiesViewModelProperty =
 			DependencyProperty.Register(nameof(DirectoryPropertiesViewModel), typeof(DirectoryPropertiesViewModel), typeof(StatusBarControl), new PropertyMetadata(null));
 
-		public SelectedItemsPropertiesViewModel SelectedItemsPropertiesViewModel
+		public SelectedItemsPropertiesViewModel? SelectedItemsPropertiesViewModel
 		{
 			get => (SelectedItemsPropertiesViewModel)GetValue(SelectedItemsPropertiesViewModelProperty);
 			set => SetValue(SelectedItemsPropertiesViewModelProperty, value);

src/Files.App/Utils/RecycleBin/RecycleBinHelpers.cs

@@ -117,10 +117,14 @@ public static async Task RestoreRecycleBinAsync()
 
 		public static async Task RestoreSelectionRecycleBinAsync(IShellPage associatedInstance)
 		{
+			var items = associatedInstance.SlimContentPage.SelectedItems;
+			if (items == null) 
+				return;
 			var ConfirmEmptyBinDialog = new ContentDialog()
 			{
 				Title = "ConfirmRestoreSelectionBinDialogTitle".GetLocalizedResource(),
-				Content = string.Format("ConfirmRestoreSelectionBinDialogContent".GetLocalizedResource(), associatedInstance.SlimContentPage.SelectedItems.Count),
+
+				Content = string.Format("ConfirmRestoreSelectionBinDialogContent".GetLocalizedResource(), items.Count),
 				PrimaryButtonText = "Yes".GetLocalizedResource(),
 				SecondaryButtonText = "Cancel".GetLocalizedResource(),
 				DefaultButton = ContentDialogButton.Primary
@@ -152,7 +156,10 @@ public static bool RecycleBinHasItems()
 
 		public static async Task RestoreItemAsync(IShellPage associatedInstance)
 		{
-			var items = associatedInstance.SlimContentPage.SelectedItems.ToList().Where(x => x is RecycleBinItem).Select((item) => new
+			var selected = associatedInstance.SlimContentPage.SelectedItems;
+			if (selected == null) 
+				return;
+			var items = selected.ToList().Where(x => x is RecycleBinItem).Select((item) => new
 			{
 				Source = StorageHelpers.FromPathAndType(
 					item.ItemPath,
@@ -164,10 +171,13 @@ public static async Task RestoreItemAsync(IShellPage associatedInstance)
 
 		public static async Task DeleteItemAsync(IShellPage associatedInstance)
 		{
-			var items = associatedInstance.SlimContentPage.SelectedItems.ToList().Select((item) => StorageHelpers.FromPathAndType(
+			var selected = associatedInstance.SlimContentPage.SelectedItems;
+			if (selected == null) 
+				return;
+			var items = selected.ToList().Select((item) => StorageHelpers.FromPathAndType(
 				item.ItemPath,
 				item.PrimaryItemAttribute == StorageItemTypes.File ? FilesystemItemType.File : FilesystemItemType.Directory));
 			await associatedInstance.FilesystemHelpers.DeleteItemsAsync(items, userSettingsService.FoldersSettingsService.DeleteConfirmationPolicy, false, true);
 		}
 	}
-}
+}

src/Files.App/Utils/Storage/History/StorageHistoryWrapper.cs

@@ -14,7 +14,7 @@ public class StorageHistoryWrapper : IDisposable
 
 		public IStorageHistory GetCurrentHistory() => histories[index];
 
-		public void AddHistory(IStorageHistory history)
+		public void AddHistory(IStorageHistory? history)
 		{
 			if (history is not null)
 			{

src/Files.App/Utils/Storage/Operations/FilesystemHelpers.cs

@@ -25,7 +25,7 @@ public sealed class FilesystemHelpers : IFilesystemHelpers
 		private readonly IJumpListService jumpListService;
 		private IFilesystemOperations filesystemOperations;
 
-		private ItemManipulationModel itemManipulationModel => associatedInstance.SlimContentPage?.ItemManipulationModel;
+		private ItemManipulationModel? itemManipulationModel => associatedInstance.SlimContentPage?.ItemManipulationModel;
 
 		private readonly CancellationToken cancellationToken;
 		private static char[] RestrictedCharacters
@@ -58,7 +58,7 @@ public FilesystemHelpers(IShellPage associatedInstance, CancellationToken cancel
 			jumpListService = Ioc.Default.GetRequiredService<IJumpListService>();
 			filesystemOperations = new ShellFilesystemOperations(this.associatedInstance);
 		}
-		public async Task<(ReturnResult, IStorageItem)> CreateAsync(IStorageItemWithPath source, bool registerHistory)
+		public async Task<(ReturnResult, IStorageItem?)> CreateAsync(IStorageItemWithPath source, bool registerHistory)
 		{
 			var returnStatus = ReturnResult.InProgress;
 			var progress = new Progress<StatusCenterItemProgressModel>();
@@ -363,7 +363,7 @@ public async Task<ReturnResult> CopyItemsFromClipboard(DataPackageView packageVi
 				ReturnResult returnStatus = ReturnResult.InProgress;
 
 				var destinations = new List<string>();
-				List<ShellFileItem> binItems = null;
+				List<ShellFileItem>? binItems = null;
 				foreach (var item in source)
 				{
 					if (RecycleBinHelpers.IsPathUnderRecycleBin(item.Path))
@@ -511,7 +511,7 @@ public async Task<ReturnResult> MoveItemsFromClipboard(DataPackageView packageVi
 			ReturnResult returnStatus = ReturnResult.InProgress;
 
 			var destinations = new List<string>();
-			List<ShellFileItem> binItems = null;
+			List<ShellFileItem>? binItems = null;
 			foreach (var item in source)
 			{
 				if (RecycleBinHelpers.IsPathUnderRecycleBin(item.Path))
@@ -551,7 +551,7 @@ await DialogDisplayHelper.ShowDialogAsync(
 				return ReturnResult.Failed;
 			}
 
-			IStorageHistory history = null;
+			IStorageHistory? history = null;
 
 			switch (source.ItemType)
 			{
@@ -658,7 +658,8 @@ public static bool IsValidForFilename(string name)
 			{
 				var itemPathOrName = string.IsNullOrEmpty(item.src.Path) ? item.src.Item.Name : item.src.Path;
 				incomingItems.Add(new FileSystemDialogConflictItemViewModel() { ConflictResolveOption = FileNameConflictResolveOptionType.None, SourcePath = itemPathOrName, DestinationPath = item.dest, DestinationDisplayName = Path.GetFileName(item.dest) });
-				if (collisions.ContainsKey(incomingItems.ElementAt(item.index).SourcePath))
+				var path = incomingItems.ElementAt(item.index).SourcePath;
+				if (path is not null && collisions.ContainsKey(path))
 				{
 					// Something strange happened, log
 					App.Logger.LogWarning($"Duplicate key when resolving conflicts: {incomingItems.ElementAt(item.index).SourcePath}, {item.src.Name}\n" +
@@ -870,6 +871,8 @@ public void Dispose()
 		{
 			filesystemOperations?.Dispose();
 
+			// SUPPRESS: Cannot convert null literal to non-nullable reference type.
+	#pragma warning disable CS8625
 			associatedInstance = null;
 			filesystemOperations = null;
 		}

src/Files.App/Utils/Storage/Operations/IFilesystemHelpers.cs

@@ -14,7 +14,7 @@ public interface IFilesystemHelpers : IDisposable
 		/// <param name="source">FullPath to the item</param>
 		/// <param name="registerHistory">Determines whether <see cref="IStorageHistory"/> is saved</param>
 		/// <returns><see cref="ReturnResult"/> of performed operation</returns>
-		Task<(ReturnResult, IStorageItem)> CreateAsync(IStorageItemWithPath source, bool registerHistory);
+		Task<(ReturnResult, IStorageItem?)> CreateAsync(IStorageItemWithPath source, bool registerHistory);
 
 		#region Delete
 

src/Files.App/ViewModels/UserControls/SidebarViewModel.cs

@@ -88,14 +88,14 @@ public SidebarDisplayMode SidebarDisplayMode
 		public bool IsSidebarCompactSize
 			=> SidebarDisplayMode == SidebarDisplayMode.Compact || SidebarDisplayMode == SidebarDisplayMode.Minimal;
 
-		public void NotifyInstanceRelatedPropertiesChanged(string arg)
+		public void NotifyInstanceRelatedPropertiesChanged(string? arg)
 		{
 			UpdateSidebarSelectedItemFromArgs(arg);
 
 			OnPropertyChanged(nameof(SidebarSelectedItem));
 		}
 
-		public void UpdateSidebarSelectedItemFromArgs(string arg)
+		public void UpdateSidebarSelectedItemFromArgs(string? arg)
 		{
 			var value = arg;
 

src/Files.App/Views/MainPage.xaml.cs

@@ -161,7 +161,7 @@ public async void TabItemContent_ContentChanged(object? sender, CustomTabViewIte
 
 			var paneArgs = e.NavigationParameter as PaneNavigationArguments;
 			SidebarAdaptiveViewModel.UpdateSidebarSelectedItemFromArgs(SidebarAdaptiveViewModel.PaneHolder.IsLeftPaneActive ?
-				paneArgs.LeftPaneNavPathParam : paneArgs.RightPaneNavPathParam);
+				paneArgs?.LeftPaneNavPathParam : paneArgs?.RightPaneNavPathParam);
 
 			UpdateStatusBarProperties();
 			LoadPaneChanged();
@@ -175,9 +175,12 @@ public void MultitaskingControl_CurrentInstanceChanged(object? sender, CurrentIn
 				SidebarAdaptiveViewModel.PaneHolder.PropertyChanged -= PaneHolder_PropertyChanged;
 
 			var navArgs = e.CurrentInstance.TabItemParameter?.NavigationParameter;
-			SidebarAdaptiveViewModel.PaneHolder = e.CurrentInstance as IPaneHolder;
-			SidebarAdaptiveViewModel.PaneHolder.PropertyChanged += PaneHolder_PropertyChanged;
-			SidebarAdaptiveViewModel.NotifyInstanceRelatedPropertiesChanged((navArgs as PaneNavigationArguments).LeftPaneNavPathParam);
+            if (e.CurrentInstance is IPaneHolder currentInstance)
+            {
+                SidebarAdaptiveViewModel.PaneHolder = currentInstance;
+                SidebarAdaptiveViewModel.PaneHolder.PropertyChanged += PaneHolder_PropertyChanged;
+			}
+			SidebarAdaptiveViewModel.NotifyInstanceRelatedPropertiesChanged((navArgs as PaneNavigationArguments)?.LeftPaneNavPathParam);
 
 			if (SidebarAdaptiveViewModel.PaneHolder?.ActivePaneOrColumn.SlimContentPage?.DirectoryPropertiesViewModel is not null)
 				SidebarAdaptiveViewModel.PaneHolder.ActivePaneOrColumn.SlimContentPage.DirectoryPropertiesViewModel.ShowLocals = true;