Resolving warnings and treating warnings as errors in WinUI project. (#824)

Directory.Packages.props

@@ -6,7 +6,7 @@
     <PackageVersion Include="ColorHashSharp" Version="1.1.0" />
     <PackageVersion Include="CommunityToolkit.Common" Version="8.4.0" />
     <PackageVersion Include="CommunityToolkit.Diagnostics" Version="8.4.0" />
-    <PackageVersion Include="CommunityToolkit.Mvvm" Version="8.4.0" />
+    <PackageVersion Include="CommunityToolkit.Mvvm" Version="8.4.1-build.4" />
     <PackageVersion Include="CommunityToolkit.WinUI.Animations" Version="8.2.251219" />
     <PackageVersion Include="CommunityToolkit.WinUI.Controls.Segmented" Version="8.2.251219" />
     <PackageVersion Include="CommunityToolkit.WinUI.Controls.SettingsControls" Version="8.2.251219" />

Wino.Core.Tests/Synchronizers/ImapSynchronizerCalDavConfigurationTests.cs

@@ -89,7 +89,7 @@ public class ImapSynchronizerCalDavConfigurationTests
 
     private static ImapSynchronizer CreateSynchronizer(string appDataFolder,
                                                        CustomServerInformation serverInformation,
-                                                       IAutoDiscoveryService autoDiscoveryService = null)
+                                                       IAutoDiscoveryService? autoDiscoveryService = null)
     {
         var account = new MailAccount
         {

Wino.Mail.WinUI/Activation/ActivationHandler.cs

@@ -18,13 +18,16 @@ public abstract class ActivationHandler<T> : ActivationHandler
 
     public override async Task HandleAsync(object args)
     {
-        await HandleInternalAsync(args as T);
+        if (args is T typedArgs)
+        {
+            await HandleInternalAsync(typedArgs);
+        }
     }
 
     public override bool CanHandle(object args)
     {
         // CanHandle checks the args is of type you have configured
-        return args is T && CanHandleInternal(args as T);
+        return args is T typedArgs && CanHandleInternal(typedArgs);
     }
 
     // You can override this method to add extra validation on activation args

Wino.Mail.WinUI/App.xaml.cs

@@ -181,7 +181,7 @@ public partial class App : WinoApplication,
         else
         {
             // Normal launch - show and activate the window.
-            MainWindow.Activate();
+            MainWindow?.Activate();
             LogActivation("Window created and activated.");
         }
     }
@@ -259,8 +259,8 @@ public partial class App : WinoApplication,
         }
         else
         {
-            MainWindow.BringToFront();
-            MainWindow.Activate();
+            MainWindow?.BringToFront();
+            MainWindow?.Activate();
         }
 
         navigationService.ChangeApplicationMode(Core.Domain.Enums.WinoApplicationMode.Calendar);
@@ -300,7 +300,7 @@ public partial class App : WinoApplication,
             // App is already running - send message and bring window to front.
             navigationService.ChangeApplicationMode(Core.Domain.Enums.WinoApplicationMode.Mail);
             WeakReferenceMessenger.Default.Send(message);
-            MainWindow.BringToFront();
+            MainWindow?.BringToFront();
         }
     }
 
@@ -405,7 +405,7 @@ public partial class App : WinoApplication,
         // Initialize theme service after window is created.
         await NewThemeService.InitializeAsync();
 
-        MainWindow.Activate();
+        MainWindow?.Activate();
         LogActivation("Window created and activated.");
     }
 

Wino.Mail.WinUI/Controls/AccountCreationDialogControl.xaml.cs

@@ -14,9 +14,9 @@ namespace Wino.Mail.WinUI.Controls;
 
 public sealed partial class AccountCreationDialogControl : UserControl, IRecipient<CopyAuthURLRequested>
 {
-    private string copyClipboardURL;
+    private string copyClipboardURL = string.Empty;
 
-    public event EventHandler CancelClicked;
+    public event EventHandler? CancelClicked;
 
     public AccountCreationDialogState State
     {
@@ -67,10 +67,10 @@ public sealed partial class AccountCreationDialogControl : UserControl, IRecipie
     {
         if (string.IsNullOrEmpty(copyClipboardURL)) return;
 
-        var clipboardService = WinoApplication.Current.Services.GetService<IClipboardService>();
+        var clipboardService = WinoApplication.Current.Services.GetRequiredService<IClipboardService>();
         await clipboardService.CopyClipboardAsync(copyClipboardURL);
     }
 
 
-    private void CancelButtonClicked(object sender, Microsoft.UI.Xaml.RoutedEventArgs e) => CancelClicked?.Invoke(this, null);
+    private void CancelButtonClicked(object sender, Microsoft.UI.Xaml.RoutedEventArgs e) => CancelClicked?.Invoke(this, EventArgs.Empty);
 }

Wino.Mail.WinUI/Controls/Calendar/CustomCalendarFlipView.cs

@@ -63,7 +63,7 @@ public partial class CustomCalendarFlipView : FlipView
     private void FlipViewSelectionChanged(object sender, SelectionChangedEventArgs e)
         => OnSelectedItemChanged(e.RemovedItems.FirstOrDefault(), e.AddedItems.FirstOrDefault());
 
-    protected virtual void OnSelectedItemChanged(object oldValue, object newValue) { }
+    protected virtual void OnSelectedItemChanged(object? oldValue, object? newValue) { }
 
     protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
     {

Wino.Mail.WinUI/Controls/Calendar/DayColumnControl.cs

@@ -18,11 +18,11 @@ public partial class DayColumnControl : Control
     private const string TodayState = nameof(TodayState);
     private const string NotTodayState = nameof(NotTodayState);
 
-    private TextBlock HeaderDateDayText;
-    private TextBlock ColumnHeaderText;
-    private Border IsTodayBorder;
-    private ItemsControl AllDayItemsControl;
-    private CalendarEventCollection _boundEventsCollection;
+    private TextBlock? HeaderDateDayText;
+    private TextBlock? ColumnHeaderText;
+    private Border? IsTodayBorder;
+    private ItemsControl? AllDayItemsControl;
+    private CalendarEventCollection? _boundEventsCollection;
 
     public CalendarDayModel DayModel
     {
@@ -97,7 +97,7 @@ public partial class DayColumnControl : Control
         _boundEventsCollection = null;
     }
 
-    private void EventsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+    private void EventsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
     {
         UpdateEventItemsSource();
     }

Wino.Mail.WinUI/Controls/Calendar/DayHeaderControl.cs

@@ -8,7 +8,7 @@ namespace Wino.Calendar.Controls;
 public partial class DayHeaderControl : Control
 {
     private const string PART_DayHeaderTextBlock = nameof(PART_DayHeaderTextBlock);
-    private TextBlock HeaderTextblock;
+    private TextBlock? HeaderTextblock;
 
     public DayHeaderDisplayType DisplayType
     {

Wino.Mail.WinUI/Controls/Calendar/WinoCalendarControl.cs

@@ -18,10 +18,10 @@ public partial class WinoCalendarControl : Control
     private const string PART_WinoFlipView = nameof(PART_WinoFlipView);
     private const string PART_IdleGrid = nameof(PART_IdleGrid);
 
-    public event EventHandler<TimelineCellSelectedArgs> TimelineCellSelected;
-    public event EventHandler<TimelineCellUnselectedArgs> TimelineCellUnselected;
+    public event EventHandler<TimelineCellSelectedArgs>? TimelineCellSelected;
+    public event EventHandler<TimelineCellUnselectedArgs>? TimelineCellUnselected;
 
-    public event EventHandler ScrollPositionChanging;
+    public event EventHandler? ScrollPositionChanging;
 
     #region Dependency Properties
 
@@ -66,8 +66,8 @@ public partial class WinoCalendarControl : Control
 
     #endregion
 
-    private WinoCalendarFlipView InternalFlipView;
-    private Grid IdleGrid;
+    private WinoCalendarFlipView? InternalFlipView;
+    private Grid? IdleGrid;
 
     private ScrollViewer? _previousScrollViewer;
     private WinoDayTimelineCanvas? _previousCanvas;
@@ -183,7 +183,7 @@ public partial class WinoCalendarControl : Control
         scrollViewer.ViewChanging -= ScrollViewChanging;
     }
 
-    private void ScrollViewChanging(object sender, ScrollViewerViewChangingEventArgs e)
+    private void ScrollViewChanging(object? sender, ScrollViewerViewChangingEventArgs e)
         => ScrollPositionChanging?.Invoke(this, EventArgs.Empty);
 
     private void CalendarSizeChanged(object sender, SizeChangedEventArgs e)
@@ -233,10 +233,10 @@ public partial class WinoCalendarControl : Control
         }
     }
 
-    private void ActiveTimelineCellUnselected(object sender, TimelineCellUnselectedArgs e)
+    private void ActiveTimelineCellUnselected(object? sender, TimelineCellUnselectedArgs e)
         => TimelineCellUnselected?.Invoke(this, e);
 
-    private void ActiveTimelineCellSelected(object sender, TimelineCellSelectedArgs e)
+    private void ActiveTimelineCellSelected(object? sender, TimelineCellSelectedArgs e)
         => TimelineCellSelected?.Invoke(this, e);
 
     public void NavigateToDay(DateTime dateTime) => InternalFlipView?.NavigateToDay(dateTime);
@@ -289,6 +289,6 @@ public partial class WinoCalendarControl : Control
 
     public CalendarItemControl GetCalendarItemControl(CalendarItemViewModel calendarItemViewModel)
     {
-        return this.FindDescendants<CalendarItemControl>().FirstOrDefault(a => a.CalendarItem == calendarItemViewModel);
+        return this.FindDescendants<CalendarItemControl>().FirstOrDefault(a => a.CalendarItem == calendarItemViewModel)!;
     }
 }

Wino.Mail.WinUI/Controls/Calendar/WinoCalendarFlipView.cs

@@ -81,7 +81,7 @@ public partial class WinoCalendarFlipView : CustomCalendarFlipView
         UpdateIdleState();
     }
 
-    protected override void OnSelectedItemChanged(object oldValue, object newValue)
+    protected override void OnSelectedItemChanged(object? oldValue, object? newValue)
     {
         base.OnSelectedItemChanged(oldValue, newValue);
 
@@ -101,7 +101,7 @@ public partial class WinoCalendarFlipView : CustomCalendarFlipView
         }
     }
 
-    private void ItemsSourceUpdated(object sender, NotifyCollectionChangedEventArgs e)
+    private void ItemsSourceUpdated(object? sender, NotifyCollectionChangedEventArgs e)
     {
         UpdateIdleState();
     }
@@ -205,7 +205,7 @@ public partial class WinoCalendarFlipView : CustomCalendarFlipView
         });
     }
 
-    private ObservableRangeCollection<DayRangeRenderModel> GetItemsSource()
+    private ObservableRangeCollection<DayRangeRenderModel>? GetItemsSource()
         => ItemsSource as ObservableRangeCollection<DayRangeRenderModel>;
 }
 

Wino.Mail.WinUI/Controls/Calendar/WinoCalendarPanel.cs

@@ -120,7 +120,7 @@ public partial class WinoCalendarPanel : Panel
 
         if (!calendarControls.Any()) return base.ArrangeOverride(finalSize);
 
-        var events = calendarControls.Select(a => a.Content as CalendarItemViewModel);
+        var events = calendarControls.Select(a => a.Content as CalendarItemViewModel).OfType<ICalendarItem>();
 
         LayoutEvents(events);
 

Wino.Mail.WinUI/Controls/Calendar/WinoCalendarTypeSelectorControl.cs

@@ -21,9 +21,9 @@ public partial class WinoCalendarTypeSelectorControl : Control
     public static readonly DependencyProperty DisplayDayCountProperty = DependencyProperty.Register(nameof(DisplayDayCount), typeof(int), typeof(WinoCalendarTypeSelectorControl), new PropertyMetadata(0));
     public static readonly DependencyProperty TodayClickedCommandProperty = DependencyProperty.Register(nameof(TodayClickedCommand), typeof(ICommand), typeof(WinoCalendarTypeSelectorControl), new PropertyMetadata(null));
 
-    public ICommand TodayClickedCommand
+    public ICommand? TodayClickedCommand
     {
-        get { return (ICommand)GetValue(TodayClickedCommandProperty); }
+        get { return (ICommand?)GetValue(TodayClickedCommandProperty); }
         set { SetValue(TodayClickedCommandProperty, value); }
     }
 
@@ -39,10 +39,10 @@ public partial class WinoCalendarTypeSelectorControl : Control
         set { SetValue(DisplayDayCountProperty, value); }
     }
 
-    private AppBarButton _todayButton;
-    private AppBarToggleButton _dayToggle;
-    private AppBarToggleButton _weekToggle;
-    private AppBarToggleButton _monthToggle;
+    private AppBarButton? _todayButton;
+    private AppBarToggleButton? _dayToggle;
+    private AppBarToggleButton? _weekToggle;
+    private AppBarToggleButton? _monthToggle;
 
     public WinoCalendarTypeSelectorControl()
     {
@@ -65,16 +65,16 @@ public partial class WinoCalendarTypeSelectorControl : Control
         Guard.IsNotNull(_weekToggle, nameof(_weekToggle));
         Guard.IsNotNull(_monthToggle, nameof(_monthToggle));
 
-        _todayButton.Click += TodayClicked;
+        _todayButton!.Click += TodayClicked;
 
-        _dayToggle.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Day); };
-        _weekToggle.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Week); };
-        _monthToggle.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Month); };
+        _dayToggle!.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Day); };
+        _weekToggle!.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Week); };
+        _monthToggle!.Click += (s, e) => { SetSelectedType(CalendarDisplayType.Month); };
 
         UpdateToggleButtonStates();
     }
 
-    private void TodayClicked(object sender, RoutedEventArgs e) => TodayClickedCommand?.Execute(null);
+    private void TodayClicked(object? sender, RoutedEventArgs e) => TodayClickedCommand?.Execute(null);
 
     private void SetSelectedType(CalendarDisplayType type)
     {

Wino.Mail.WinUI/Controls/Calendar/WinoCalendarView.cs

@@ -18,7 +18,7 @@ public partial class WinoCalendarView : Control
     public static readonly DependencyProperty HighlightedDateRangeProperty = DependencyProperty.Register(nameof(HighlightedDateRange), typeof(DateRange), typeof(WinoCalendarView), new PropertyMetadata(null, new PropertyChangedCallback(OnHighlightedDateRangeChanged)));
     public static readonly DependencyProperty VisibleDateBackgroundProperty = DependencyProperty.Register(nameof(VisibleDateBackground), typeof(Brush), typeof(WinoCalendarView), new PropertyMetadata(null, new PropertyChangedCallback(OnPropertiesChanged)));
     public static readonly DependencyProperty DateClickedCommandProperty = DependencyProperty.Register(nameof(DateClickedCommand), typeof(ICommand), typeof(WinoCalendarView), new PropertyMetadata(null));
-    public static readonly DependencyProperty TodayBackgroundColorProperty = DependencyProperty.Register(nameof(TodayBackgroundColor), typeof(Color), typeof(WinoCalendarView), new PropertyMetadata(null));
+    public static readonly DependencyProperty TodayBackgroundColorProperty = DependencyProperty.Register(nameof(TodayBackgroundColor), typeof(Color), typeof(WinoCalendarView), new PropertyMetadata(new Color()));
 
     public Color TodayBackgroundColor
     {
@@ -30,30 +30,30 @@ public partial class WinoCalendarView : Control
     /// Gets or sets the command to execute when a date is picked.
     /// Unused.
     /// </summary>
-    public ICommand DateClickedCommand
+    public ICommand? DateClickedCommand
     {
-        get { return (ICommand)GetValue(DateClickedCommandProperty); }
+        get { return (ICommand?)GetValue(DateClickedCommandProperty); }
         set { SetValue(DateClickedCommandProperty, value); }
     }
 
     /// <summary>
     /// Gets or sets the highlighted range of dates.
     /// </summary>
-    public DateRange HighlightedDateRange
+    public DateRange? HighlightedDateRange
     {
-        get { return (DateRange)GetValue(HighlightedDateRangeProperty); }
+        get { return (DateRange?)GetValue(HighlightedDateRangeProperty); }
         set { SetValue(HighlightedDateRangeProperty, value); }
     }
 
-    public Brush VisibleDateBackground
+    public Brush? VisibleDateBackground
     {
-        get { return (Brush)GetValue(VisibleDateBackgroundProperty); }
+        get { return (Brush?)GetValue(VisibleDateBackgroundProperty); }
         set { SetValue(VisibleDateBackgroundProperty, value); }
     }
 
 
 
-    private CalendarView CalendarView;
+    private CalendarView? CalendarView;
 
     public WinoCalendarView()
     {
@@ -67,6 +67,7 @@ public partial class WinoCalendarView : Control
         CalendarView = GetTemplateChild(PART_CalendarView) as CalendarView;
 
         Guard.IsNotNull(CalendarView, nameof(CalendarView));
+        if (CalendarView == null) return;
 
         CalendarView.SelectedDatesChanged -= InternalCalendarViewSelectionChanged;
         CalendarView.SelectedDatesChanged += InternalCalendarViewSelectionChanged;
@@ -92,7 +93,7 @@ public partial class WinoCalendarView : Control
         }
 
         // Reset selection, we don't show selected dates but react to them.
-        CalendarView.SelectedDates.Clear();
+        CalendarView?.SelectedDates.Clear();
     }
 
     private static void OnPropertiesChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
@@ -107,7 +108,7 @@ public partial class WinoCalendarView : Control
 
     // Changing selected dates will trigger the selection changed event.
     // It will behave like user clicked the date.
-    public void GoToDay(DateTime dateTime) => CalendarView.SelectedDates.Add(dateTime);
+    public void GoToDay(DateTime dateTime) => CalendarView?.SelectedDates.Add(dateTime);
 
     private static void OnHighlightedDateRangeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
     {

Wino.Mail.WinUI/Controls/Calendar/WinoDayTimelineCanvas.cs

@@ -17,11 +17,11 @@ namespace Wino.Calendar.Controls;
 
 public partial class WinoDayTimelineCanvas : Control, IDisposable
 {
-    public event EventHandler<TimelineCellSelectedArgs> TimelineCellSelected;
-    public event EventHandler<TimelineCellUnselectedArgs> TimelineCellUnselected;
+    public event EventHandler<TimelineCellSelectedArgs>? TimelineCellSelected;
+    public event EventHandler<TimelineCellUnselectedArgs>? TimelineCellUnselected;
 
     private const string PART_InternalCanvas = nameof(PART_InternalCanvas);
-    private SKXamlCanvas Canvas;
+    private SKXamlCanvas? Canvas;
 
     public static readonly DependencyProperty RenderOptionsProperty = DependencyProperty.Register(nameof(RenderOptions), typeof(CalendarRenderOptions), typeof(WinoDayTimelineCanvas), new PropertyMetadata(null, new PropertyChangedCallback(OnRenderingPropertiesChanged)));
     public static readonly DependencyProperty SeperatorColorProperty = DependencyProperty.Register(nameof(SeperatorColor), typeof(SolidColorBrush), typeof(WinoDayTimelineCanvas), new PropertyMetadata(null, new PropertyChangedCallback(OnRenderingPropertiesChanged)));
@@ -31,39 +31,39 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
     public static readonly DependencyProperty SelectedDateTimeProperty = DependencyProperty.Register(nameof(SelectedDateTime), typeof(DateTime?), typeof(WinoDayTimelineCanvas), new PropertyMetadata(null, new PropertyChangedCallback(OnSelectedDateTimeChanged)));
     public static readonly DependencyProperty PositionerUIElementProperty = DependencyProperty.Register(nameof(PositionerUIElement), typeof(UIElement), typeof(WinoDayTimelineCanvas), new PropertyMetadata(null));
 
-    public UIElement PositionerUIElement
+    public UIElement? PositionerUIElement
     {
-        get { return (UIElement)GetValue(PositionerUIElementProperty); }
+        get { return (UIElement?)GetValue(PositionerUIElementProperty); }
         set { SetValue(PositionerUIElementProperty, value); }
     }
 
-    public CalendarRenderOptions RenderOptions
+    public CalendarRenderOptions? RenderOptions
     {
-        get { return (CalendarRenderOptions)GetValue(RenderOptionsProperty); }
+        get { return (CalendarRenderOptions?)GetValue(RenderOptionsProperty); }
         set { SetValue(RenderOptionsProperty, value); }
     }
 
-    public SolidColorBrush HalfHourSeperatorColor
+    public SolidColorBrush? HalfHourSeperatorColor
     {
-        get { return (SolidColorBrush)GetValue(HalfHourSeperatorColorProperty); }
+        get { return (SolidColorBrush?)GetValue(HalfHourSeperatorColorProperty); }
         set { SetValue(HalfHourSeperatorColorProperty, value); }
     }
 
-    public SolidColorBrush SeperatorColor
+    public SolidColorBrush? SeperatorColor
     {
-        get { return (SolidColorBrush)GetValue(SeperatorColorProperty); }
+        get { return (SolidColorBrush?)GetValue(SeperatorColorProperty); }
         set { SetValue(SeperatorColorProperty, value); }
     }
 
-    public SolidColorBrush WorkingHourCellBackgroundColor
+    public SolidColorBrush? WorkingHourCellBackgroundColor
     {
-        get { return (SolidColorBrush)GetValue(WorkingHourCellBackgroundColorProperty); }
+        get { return (SolidColorBrush?)GetValue(WorkingHourCellBackgroundColorProperty); }
         set { SetValue(WorkingHourCellBackgroundColorProperty, value); }
     }
 
-    public SolidColorBrush SelectedCellBackgroundBrush
+    public SolidColorBrush? SelectedCellBackgroundBrush
     {
-        get { return (SolidColorBrush)GetValue(SelectedCellBackgroundBrushProperty); }
+        get { return (SolidColorBrush?)GetValue(SelectedCellBackgroundBrushProperty); }
         set { SetValue(SelectedCellBackgroundBrushProperty, value); }
     }
 
@@ -106,9 +106,11 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
         TimelineCellUnselected?.Invoke(this, new TimelineCellUnselectedArgs());
     }
 
-    private void OnCanvasPointerPressed(object sender, PointerRoutedEventArgs e)
+    private void OnCanvasPointerPressed(object? sender, PointerRoutedEventArgs e)
     {
         if (RenderOptions == null) return;
+        var canvas = Canvas;
+        if (canvas == null) return;
 
         var hourHeight = RenderOptions.CalendarSettings.HourHeight;
 
@@ -119,12 +121,15 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
             PositionerUIElement = this.FindParents().LastOrDefault(a => a is Grid);
         }
 
+        if (PositionerUIElement == null)
+            return;
+
         PointerPoint positionerRootPoint = e.GetCurrentPoint(PositionerUIElement);
-        PointerPoint canvasPointerPoint = e.GetCurrentPoint(Canvas);
+        PointerPoint canvasPointerPoint = e.GetCurrentPoint(canvas);
 
         Point touchPoint = canvasPointerPoint.Position;
 
-        var singleDayWidth = (Canvas.ActualWidth / RenderOptions.TotalDayCount);
+        var singleDayWidth = (canvas.ActualWidth / RenderOptions.TotalDayCount);
 
         int day = (int)(touchPoint.X / singleDayWidth);
         int hour = (int)(touchPoint.Y / hourHeight);
@@ -187,9 +192,14 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
             && SelectedCellBackgroundBrush != null;
     }
 
-    private void OnCanvasPaintSurface(object sender, SKPaintSurfaceEventArgs e)
+    private void OnCanvasPaintSurface(object? sender, SKPaintSurfaceEventArgs e)
     {
         if (!CanDrawTimeline()) return;
+        var renderOptions = RenderOptions!;
+        var workingHourCellBackgroundColor = WorkingHourCellBackgroundColor!;
+        var seperatorColor = SeperatorColor!;
+        var halfHourSeperatorColor = HalfHourSeperatorColor!;
+        var selectedCellBackgroundBrush = SelectedCellBackgroundBrush!;
 
         var canvas = e.Surface.Canvas;
         canvas.Clear(SKColors.Transparent);
@@ -203,13 +213,13 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
 
         // Calculate the width of each rectangle (1 day column)
         // Equal distribution of the whole width.
-        double rectWidth = canvasWidth / RenderOptions.TotalDayCount;
+        double rectWidth = canvasWidth / renderOptions.TotalDayCount;
 
         // Calculate the height of each rectangle (1 hour row)
-        double rectHeight = RenderOptions.CalendarSettings.HourHeight;
+        double rectHeight = renderOptions.CalendarSettings.HourHeight;
 
         // Define stroke and fill colors
-        var strokeColor = ToSKColor(SeperatorColor.Color);
+        var strokeColor = ToSKColor(seperatorColor.Color);
         float strokeThickness = 0.5f;
 
         // Create paints for drawing
@@ -229,18 +239,18 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
 
         using var dashedPaint = new SKPaint
         {
-            Color = ToSKColor(HalfHourSeperatorColor.Color),
+            Color = ToSKColor(halfHourSeperatorColor.Color),
             StrokeWidth = strokeThickness,
             Style = SKPaintStyle.Stroke,
             PathEffect = SKPathEffect.CreateDash([2f, 2f], 0),
             IsAntialias = true
         };
 
-        for (int day = 0; day < RenderOptions.TotalDayCount; day++)
+        for (int day = 0; day < renderOptions.TotalDayCount; day++)
         {
-            var currentDay = RenderOptions.DateRange.StartDate.AddDays(day);
+            var currentDay = renderOptions.DateRange.StartDate.AddDays(day);
 
-            bool isWorkingDay = RenderOptions.CalendarSettings.WorkingDays.Contains(currentDay.DayOfWeek);
+            bool isWorkingDay = renderOptions.CalendarSettings.WorkingDays.Contains(currentDay.DayOfWeek);
 
             // Loop through each hour (rows)
             for (int hour = 0; hour < hours; hour++)
@@ -263,12 +273,12 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
 
                 // Fill another rectangle with the working hour background color
                 // This rectangle must be placed with -1 margin to prevent invisible borders of the main rectangle.
-                if (isWorkingDay && renderTime >= RenderOptions.CalendarSettings.WorkingHourStart && renderTime <= RenderOptions.CalendarSettings.WorkingHourEnd)
+                if (isWorkingDay && renderTime >= renderOptions.CalendarSettings.WorkingHourStart && renderTime <= renderOptions.CalendarSettings.WorkingHourEnd)
                 {
                     var backgroundRectangle = new SKRect(x + 1, y + 1, x + width - 1, y + height - 1);
 
                     canvas.DrawRect(backgroundRectangle, strokePaint);
-                    fillPaint.Color = ToSKColor(WorkingHourCellBackgroundColor.Color);
+                    fillPaint.Color = ToSKColor(workingHourCellBackgroundColor.Color);
                     canvas.DrawRect(backgroundRectangle, fillPaint);
                 }
 
@@ -298,7 +308,7 @@ public partial class WinoDayTimelineCanvas : Control, IDisposable
                         (float)(day * rectWidth + rectWidth),
                         (float)(selectedY + selectionRectHeight));
 
-                    fillPaint.Color = ToSKColor(SelectedCellBackgroundBrush.Color);
+                    fillPaint.Color = ToSKColor(selectedCellBackgroundBrush.Color);
                     canvas.DrawRect(selectedRectangle, fillPaint);
                 }
             }

Wino.Mail.WinUI/Controls/WinoInfoBar.cs

@@ -71,7 +71,7 @@ public partial class WinoInfoBar : InfoBar
         }
     }
 
-    private async void TimerTick(object sender, object e)
+    private async void TimerTick(object? sender, object e)
     {
         _dispatcherTimer.Stop();
         _dispatcherTimer.Tick -= TimerTick;

Wino.Mail.WinUI/Dialogs/AccountCreationDialog.xaml.cs

@@ -10,7 +10,7 @@ namespace Wino.Dialogs;
 public sealed partial class AccountCreationDialog : ContentDialog, IAccountCreationDialog
 {
     private TaskCompletionSource<bool> dialogOpened = new TaskCompletionSource<bool>();
-    public CancellationTokenSource CancellationTokenSource { get; private set; }
+    public CancellationTokenSource? CancellationTokenSource { get; private set; }
 
     public AccountCreationDialogState State
     {
@@ -41,7 +41,7 @@ public sealed partial class AccountCreationDialog : ContentDialog, IAccountCreat
         // Unregister from closing event.
         Closing -= DialogClosing;
 
-        if (cancel && !CancellationTokenSource.IsCancellationRequested)
+        if (cancel && CancellationTokenSource != null && !CancellationTokenSource.IsCancellationRequested)
         {
             CancellationTokenSource.Cancel();
         }

Wino.Mail.WinUI/Dialogs/AccountPickerDialog.xaml.cs

@@ -6,9 +6,9 @@ namespace Wino.Dialogs;
 
 public sealed partial class AccountPickerDialog : ContentDialog
 {
-    public MailAccount PickedAccount { get; set; }
+    public MailAccount? PickedAccount { get; set; }
 
-    public List<MailAccount> AvailableAccounts { get; set; }
+    public List<MailAccount> AvailableAccounts { get; set; } = [];
 
     public AccountPickerDialog(List<MailAccount> availableAccounts)
     {

Wino.Mail.WinUI/Dialogs/CustomThemeBuilderDialog.xaml.cs

@@ -10,21 +10,21 @@ namespace Wino.Dialogs;
 
 public sealed partial class CustomThemeBuilderDialog : ContentDialog
 {
-    public byte[] WallpaperData { get; private set; }
-    public string AccentColor { get; private set; }
+    public byte[] WallpaperData { get; private set; } = Array.Empty<byte>();
+    public string AccentColor { get; private set; } = string.Empty;
 
-    private INewThemeService _themeService;
+    private readonly INewThemeService _themeService;
 
     public CustomThemeBuilderDialog()
     {
         InitializeComponent();
 
-        _themeService = WinoApplication.Current.Services.GetService<INewThemeService>();
+        _themeService = WinoApplication.Current.Services.GetRequiredService<INewThemeService>();
     }
 
     private async void ApplyClicked(ContentDialog sender, ContentDialogButtonClickEventArgs args)
     {
-        if (Array.Empty<byte>() == WallpaperData)
+        if (WallpaperData.Length == 0)
             return;
 
         var deferal = args.GetDeferral();
@@ -45,11 +45,11 @@ public sealed partial class CustomThemeBuilderDialog : ContentDialog
 
     private async void BrowseWallpaperClicked(object sender, Microsoft.UI.Xaml.RoutedEventArgs e)
     {
-        var dialogService = WinoApplication.Current.Services.GetService<IMailDialogService>();
+        var dialogService = WinoApplication.Current.Services.GetRequiredService<IMailDialogService>();
 
         var pickedFileData = await dialogService.PickWindowsFileContentAsync(".jpg", ".png");
 
-        if (pickedFileData == Array.Empty<byte>()) return;
+        if (pickedFileData.Length == 0) return;
 
         IsPrimaryButtonEnabled = true;
 

Wino.Mail.WinUI/Dialogs/NewAccountDialog.xaml.cs

@@ -15,7 +15,7 @@ namespace Wino.Mail.WinUI.Dialogs;
 
 public sealed partial class NewAccountDialog : ContentDialog
 {
-    private Dictionary<SpecialImapProvider, string> helpingLinks = new Dictionary<SpecialImapProvider, string>()
+    private readonly Dictionary<SpecialImapProvider, string> helpingLinks = new Dictionary<SpecialImapProvider, string>()
     {
         { SpecialImapProvider.iCloud, "https://support.apple.com/en-us/102654" },
         { SpecialImapProvider.Yahoo, "http://help.yahoo.com/kb/SLN15241.html" },
@@ -28,9 +28,9 @@ public sealed partial class NewAccountDialog : ContentDialog
     public static readonly DependencyProperty SelectedCalendarModeIndexProperty = DependencyProperty.Register(nameof(SelectedCalendarModeIndex), typeof(int), typeof(NewAccountDialog), new PropertyMetadata(0));
 
 
-    public AppColorViewModel SelectedColor
+    public AppColorViewModel? SelectedColor
     {
-        get { return (AppColorViewModel)GetValue(SelectedColorProperty); }
+        get { return (AppColorViewModel?)GetValue(SelectedColorProperty); }
         set { SetValue(SelectedColorProperty, value); }
     }
 
@@ -43,9 +43,9 @@ public sealed partial class NewAccountDialog : ContentDialog
     /// <summary>
     /// Gets or sets current selected mail provider in the dialog.
     /// </summary>
-    public ProviderDetail SelectedMailProvider
+    public ProviderDetail? SelectedMailProvider
     {
-        get { return (ProviderDetail)GetValue(SelectedMailProviderProperty); }
+        get { return (ProviderDetail?)GetValue(SelectedMailProviderProperty); }
         set { SetValue(SelectedMailProviderProperty, value); }
     }
 
@@ -64,9 +64,9 @@ public sealed partial class NewAccountDialog : ContentDialog
 
     // List of available mail providers for now.
 
-    public List<IProviderDetail> Providers { get; set; }
+    public List<IProviderDetail> Providers { get; set; } = [];
 
-    public List<AppColorViewModel> AvailableColors { get; set; }
+    public List<AppColorViewModel> AvailableColors { get; set; } = [];
     public List<string> CalendarModeOptions { get; } =
     [
         Translator.ImapCalDavSettingsPage_CalendarModeCalDav,
@@ -75,7 +75,7 @@ public sealed partial class NewAccountDialog : ContentDialog
     ];
 
 
-    public AccountCreationDialogResult Result = null;
+    public AccountCreationDialogResult? Result = null;
 
     public NewAccountDialog()
     {
@@ -113,6 +113,9 @@ public sealed partial class NewAccountDialog : ContentDialog
 
     private void CreateClicked(ContentDialog sender, ContentDialogButtonClickEventArgs args)
     {
+        if (SelectedMailProvider == null)
+            return;
+
         if (IsSpecialImapServerPartVisible)
         {
             // Special imap detail input.
@@ -198,7 +201,11 @@ public sealed partial class NewAccountDialog : ContentDialog
 
     private async void AppSpecificHelpButtonClicked(object sender, RoutedEventArgs e)
     {
-        var helpUrl = helpingLinks[SelectedMailProvider.SpecialImapProvider];
+        if (SelectedMailProvider == null ||
+            !helpingLinks.TryGetValue(SelectedMailProvider.SpecialImapProvider, out var helpUrl))
+        {
+            return;
+        }
 
         await Launcher.LaunchUriAsync(new Uri(helpUrl));
     }

Wino.Mail.WinUI/Dialogs/PrintDialog.xaml.cs

@@ -25,7 +25,7 @@ public sealed partial class PrintDialog : ContentDialog
     /// Initializes the dialog with existing print settings.
     /// </summary>
     /// <param name="printSettings">The initial print settings to load.</param>
-    public PrintDialog(WebView2PrintSettingsModel printSettings = null)
+    public PrintDialog(WebView2PrintSettingsModel printSettings = default!)
     {
         if (printSettings != null) PrintSettings = printSettings;
 

Wino.Mail.WinUI/Extensions/AnimationExtensions.cs

@@ -76,7 +76,7 @@ public static class AnimationExtensions
 
     public static void Animate(this DependencyObject target, double? from, double to,
       string propertyPath, int duration = 400, int startTime = 0,
-      EasingFunctionBase easing = null, Action completed = null, bool enableDependentAnimation = false)
+      EasingFunctionBase? easing = null, Action? completed = null, bool enableDependentAnimation = false)
     {
         if (easing == null)
         {

Wino.Mail.WinUI/Extensions/CompositionExtensions.Implicit.cs

@@ -17,12 +17,12 @@ public static partial class CompositionExtensions
         var compositor = elementVisual.Compositor;
         ElementCompositionPreview.SetIsTranslationEnabled(element, true);
 
-        ScalarKeyFrameAnimation hideOpacityAnimation = null;
-        ScalarKeyFrameAnimation showOpacityAnimation = null;
-        ScalarKeyFrameAnimation hideOffsetAnimation = null;
-        ScalarKeyFrameAnimation showOffsetAnimation = null;
-        Vector2KeyFrameAnimation hideScaleAnimation = null;
-        Vector2KeyFrameAnimation showeScaleAnimation = null;
+        ScalarKeyFrameAnimation? hideOpacityAnimation = null;
+        ScalarKeyFrameAnimation? showOpacityAnimation = null;
+        ScalarKeyFrameAnimation? hideOffsetAnimation = null;
+        ScalarKeyFrameAnimation? showOffsetAnimation = null;
+        Vector2KeyFrameAnimation? hideScaleAnimation = null;
+        Vector2KeyFrameAnimation? showeScaleAnimation = null;
 
         if (animateOpacity)
         {
@@ -119,7 +119,7 @@ public static partial class CompositionExtensions
     }
 
     public static void EnableImplicitAnimation(this UIElement element, VisualPropertyType typeToAnimate,
-        double duration = 800, double delay = 0, CompositionEasingFunction easing = null)
+        double duration = 800, double delay = 0, CompositionEasingFunction? easing = null)
     {
         var visual = element.Visual();
         var compositor = visual.Compositor;
@@ -142,7 +142,7 @@ public static partial class CompositionExtensions
     }
 
     public static void EnableImplicitAnimation(this Visual visual, VisualPropertyType typeToAnimate,
-        double duration = 800, double delay = 0, CompositionEasingFunction easing = null)
+        double duration = 800, double delay = 0, CompositionEasingFunction? easing = null)
     {
         var compositor = visual.Compositor;
 
@@ -163,8 +163,8 @@ public static partial class CompositionExtensions
         visual.ImplicitAnimations = animationCollection;
     }
 
-    private static KeyFrameAnimation CreateAnimationByType(Compositor compositor, VisualPropertyType type,
-        double duration = 800, double delay = 0, CompositionEasingFunction easing = null)
+    private static KeyFrameAnimation? CreateAnimationByType(Compositor compositor, VisualPropertyType type,
+        double duration = 800, double delay = 0, CompositionEasingFunction? easing = null)
     {
         KeyFrameAnimation animation;
 

Wino.Mail.WinUI/Extensions/UtilExtensions.cs

@@ -22,9 +22,9 @@ public static class UtilExtensions
         {
             var child = VisualTreeHelper.GetChild(parent, i);
 
-            if (child is FrameworkElement)
+            if (child is FrameworkElement frameworkElement)
             {
-                list.Add(child as FrameworkElement);
+                list.Add(frameworkElement);
             }
 
             list.AddRange(Children(child));
@@ -33,20 +33,13 @@ public static class UtilExtensions
         return list;
     }
 
-    public static T GetChildByName<T>(this DependencyObject parent, string name)
+    public static T? GetChildByName<T>(this DependencyObject parent, string name) where T : class
     {
         var childControls = Children(parent);
         var controls = childControls.OfType<FrameworkElement>();
 
-        if (controls == null)
-        {
-            return default(T);
-        }
-
         var control = controls
-            .Where(x => x.Name.Equals(name))
-            .Cast<T>()
-            .First();
+            .FirstOrDefault(x => x.Name.Equals(name)) as T;
 
         return control;
     }

Wino.Mail.WinUI/Helpers/CalendarXamlHelpers.cs

@@ -15,7 +15,7 @@ namespace Wino.Calendar.Helpers;
 public static class CalendarXamlHelpers
 {
     public static CalendarItemViewModel GetFirstAllDayEvent(CalendarEventCollection collection)
-        => (CalendarItemViewModel)collection.AllDayEvents.FirstOrDefault();
+        => collection.AllDayEvents.OfType<CalendarItemViewModel>().FirstOrDefault()!;
 
     /// <summary>
     /// Returns full date + duration info in Event Details page details title.

Wino.Mail.WinUI/Helpers/WinoVisualTreeHelper.cs

@@ -6,18 +6,20 @@ namespace Wino.Helpers;
 
 public static class WinoVisualTreeHelper
 {
-    public static T GetChildObject<T>(DependencyObject obj, string name) where T : FrameworkElement
+    public static T? GetChildObject<T>(DependencyObject? obj, string name) where T : FrameworkElement
     {
-        DependencyObject child = null;
-        T grandChild = null;
+        if (obj == null) return null;
+
+        DependencyObject? child = null;
+        T? grandChild = null;
 
         for (int i = 0; i <= VisualTreeHelper.GetChildrenCount(obj) - 1; i++)
         {
             child = VisualTreeHelper.GetChild(obj, i);
 
-            if (child is T && (((T)child).Name == name | string.IsNullOrEmpty(name)))
+            if (child is T typedChild && (typedChild.Name == name || string.IsNullOrEmpty(name)))
             {
-                return (T)child;
+                return typedChild;
             }
             else
             {
@@ -31,7 +33,7 @@ public static class WinoVisualTreeHelper
         return null;
     }
 
-    public static IEnumerable<T> FindDescendants<T>(this DependencyObject depObj) where T : DependencyObject
+    public static IEnumerable<T> FindDescendants<T>(this DependencyObject? depObj) where T : DependencyObject
     {
         if (depObj != null)
         {

Wino.Mail.WinUI/Helpers/XamlHelpers.cs

@@ -51,7 +51,7 @@ public static class XamlHelpers
     public static ListViewSelectionMode BoolToSelectionMode(bool isSelectionMode) => isSelectionMode ? ListViewSelectionMode.Multiple : ListViewSelectionMode.None;
     public static string BoolToSelectionModeText(bool isSelectionMode) => isSelectionMode ? Translator.Buttons_Cancel : Translator.Buttons_Multiselect;
 
-    public static Microsoft.UI.Xaml.Media.Imaging.BitmapImage Base64ToBitmapImage(string base64String)
+    public static Microsoft.UI.Xaml.Media.Imaging.BitmapImage? Base64ToBitmapImage(string base64String)
     {
         if (string.IsNullOrEmpty(base64String))
             return null;
@@ -154,7 +154,7 @@ public static class XamlHelpers
         if (groupObject is string stringObject)
             return stringObject;
 
-        object dateObject = null;
+        object? dateObject = null;
 
         // From regular mail header template
         if (groupObject is DateTime groupedDate)
@@ -180,7 +180,7 @@ public static class XamlHelpers
 
             }
             else
-                return dateObject.ToString();
+                return dateObject.ToString() ?? string.Empty;
         }
 
         return Translator.UnknownDateHeader;
@@ -321,6 +321,10 @@ public static class XamlHelpers
         "xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'>" +
         "<Path.Data>" + pathMarkup + "</Path.Data></Path>";
         var path = XamlReader.Load(xaml) as Microsoft.UI.Xaml.Shapes.Path;
+        if (path?.Data == null)
+        {
+            return new PathGeometry();
+        }
 
         Geometry geometry = path.Data;
         path.Data = null;

Wino.Mail.WinUI/Models/PrintDialogViewModel.cs

@@ -17,7 +17,7 @@ public class PrintDialogViewModel : INotifyPropertyChanged
     private bool _isCustomPageRange = false;
     private WebView2PrintSettingsModel _printSettings = new();
 
-    public event PropertyChangedEventHandler PropertyChanged;
+    public event PropertyChangedEventHandler? PropertyChanged;
 
     public PrintDialogViewModel()
     {
@@ -208,7 +208,7 @@ public class PrintDialogViewModel : INotifyPropertyChanged
     /// Initializes the dialog with the provided print settings.
     /// </summary>
     /// <param name="printSettings">The initial print settings.</param>
-    public void Initialize(WebView2PrintSettingsModel printSettings = null)
+    public void Initialize(WebView2PrintSettingsModel printSettings = default!)
     {
         if (printSettings != null)
         {
@@ -237,7 +237,7 @@ public class PrintDialogViewModel : INotifyPropertyChanged
         }
     }
 
-    private void OnPrintSettingsChanged(object sender, PropertyChangedEventArgs e)
+    private void OnPrintSettingsChanged(object? sender, PropertyChangedEventArgs e)
     {
         if (e.PropertyName == nameof(WebView2PrintSettingsModel.ScaleFactor))
         {

Wino.Mail.WinUI/Selectors/AppThemePreviewTemplateSelector.cs

@@ -6,9 +6,9 @@ namespace Wino.Mail.WinUI.Selectors;
 
 public partial class AppThemePreviewTemplateSelector : DataTemplateSelector
 {
-    public DataTemplate SystemThemeTemplate { get; set; }
-    public DataTemplate PreDefinedThemeTemplate { get; set; }
-    public DataTemplate CustomAppTemplate { get; set; }
+    public DataTemplate SystemThemeTemplate { get; set; } = null!;
+    public DataTemplate PreDefinedThemeTemplate { get; set; } = null!;
+    public DataTemplate CustomAppTemplate { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item)
     {
@@ -19,6 +19,6 @@ public partial class AppThemePreviewTemplateSelector : DataTemplateSelector
         else if (item is CustomAppTheme)
             return CustomAppTemplate;
 
-        return base.SelectTemplateCore(item);
+        return base.SelectTemplateCore(item) ?? SystemThemeTemplate;
     }
 }

Wino.Mail.WinUI/Selectors/CalendarItemShowAsStripeTemplateSelector.cs

@@ -10,11 +10,11 @@ namespace Wino.Selectors;
 /// </summary>
 public partial class CalendarItemShowAsStripeTemplateSelector : DataTemplateSelector
 {
-    public DataTemplate FreeTemplate { get; set; }
-    public DataTemplate TentativeTemplate { get; set; }
-    public DataTemplate BusyTemplate { get; set; }
-    public DataTemplate OutOfOfficeTemplate { get; set; }
-    public DataTemplate WorkingElsewhereTemplate { get; set; }
+    public DataTemplate FreeTemplate { get; set; } = null!;
+    public DataTemplate TentativeTemplate { get; set; } = null!;
+    public DataTemplate BusyTemplate { get; set; } = null!;
+    public DataTemplate OutOfOfficeTemplate { get; set; } = null!;
+    public DataTemplate WorkingElsewhereTemplate { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
     {
@@ -31,6 +31,6 @@ public partial class CalendarItemShowAsStripeTemplateSelector : DataTemplateSele
             };
         }
 
-        return base.SelectTemplateCore(item, container);
+        return base.SelectTemplateCore(item, container) ?? BusyTemplate;
     }
 }

Wino.Mail.WinUI/Selectors/CustomWinoMessageDialogIconSelector.cs

@@ -7,14 +7,14 @@ namespace Wino.Mail.WinUI.Selectors;
 
 public partial class CustomWinoMessageDialogIconSelector : DataTemplateSelector
 {
-    public DataTemplate InfoIconTemplate { get; set; }
-    public DataTemplate WarningIconTemplate { get; set; }
-    public DataTemplate QuestionIconTemplate { get; set; }
-    public DataTemplate ErrorIconTemplate { get; set; }
+    public DataTemplate InfoIconTemplate { get; set; } = null!;
+    public DataTemplate WarningIconTemplate { get; set; } = null!;
+    public DataTemplate QuestionIconTemplate { get; set; } = null!;
+    public DataTemplate ErrorIconTemplate { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
     {
-        if (item == null) return null;
+        if (item == null) return InfoIconTemplate;
 
         if (item is WinoCustomMessageDialogIcon icon)
         {
@@ -32,6 +32,6 @@ public partial class CustomWinoMessageDialogIconSelector : DataTemplateSelector
                     throw new Exception("Unknown custom message dialog icon.");
             }
         }
-        return base.SelectTemplateCore(item, container);
+        return base.SelectTemplateCore(item, container) ?? InfoIconTemplate;
     }
 }

Wino.Mail.WinUI/Selectors/FileAttachmentTypeSelector.cs

@@ -6,16 +6,16 @@ namespace Wino.Mail.WinUI.Selectors;
 
 public partial class FileAttachmentTypeSelector : DataTemplateSelector
 {
-    public DataTemplate None { get; set; }
-    public DataTemplate Executable { get; set; }
-    public DataTemplate Image { get; set; }
-    public DataTemplate Audio { get; set; }
-    public DataTemplate Video { get; set; }
-    public DataTemplate PDF { get; set; }
-    public DataTemplate HTML { get; set; }
-    public DataTemplate RarArchive { get; set; }
-    public DataTemplate Archive { get; set; }
-    public DataTemplate Other { get; set; }
+    public DataTemplate None { get; set; } = null!;
+    public DataTemplate Executable { get; set; } = null!;
+    public DataTemplate Image { get; set; } = null!;
+    public DataTemplate Audio { get; set; } = null!;
+    public DataTemplate Video { get; set; } = null!;
+    public DataTemplate PDF { get; set; } = null!;
+    public DataTemplate HTML { get; set; } = null!;
+    public DataTemplate RarArchive { get; set; } = null!;
+    public DataTemplate Archive { get; set; } = null!;
+    public DataTemplate Other { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
     {

Wino.Mail.WinUI/Selectors/NavigationMenuTemplateSelector.cs

@@ -6,23 +6,23 @@ namespace Wino.Mail.WinUI.Selectors;
 
 public partial class NavigationMenuTemplateSelector : DataTemplateSelector
 {
-    public DataTemplate MenuItemTemplate { get; set; }
-    public DataTemplate ContactsMenuItemTemplate { get; set; }
-    public DataTemplate AccountManagementTemplate { get; set; }
-    public DataTemplate ClickableAccountMenuTemplate { get; set; }
-    public DataTemplate MergedAccountTemplate { get; set; }
-    public DataTemplate MergedAccountFolderTemplate { get; set; }
-    public DataTemplate MergedAccountMoreExpansionItemTemplate { get; set; }
-    public DataTemplate FolderMenuTemplate { get; set; }
-    public DataTemplate SettingsItemTemplate { get; set; }
-    public DataTemplate MoreItemsFolderTemplate { get; set; }
-    public DataTemplate RatingItemTemplate { get; set; }
-    public DataTemplate CreateNewFolderTemplate { get; set; }
-    public DataTemplate SeperatorTemplate { get; set; }
-    public DataTemplate NewMailTemplate { get; set; }
-    public DataTemplate CategoryItemsTemplate { get; set; }
-    public DataTemplate FixAuthenticationIssueTemplate { get; set; }
-    public DataTemplate FixMissingFolderConfigTemplate { get; set; }
+    public DataTemplate MenuItemTemplate { get; set; } = null!;
+    public DataTemplate ContactsMenuItemTemplate { get; set; } = null!;
+    public DataTemplate AccountManagementTemplate { get; set; } = null!;
+    public DataTemplate ClickableAccountMenuTemplate { get; set; } = null!;
+    public DataTemplate MergedAccountTemplate { get; set; } = null!;
+    public DataTemplate MergedAccountFolderTemplate { get; set; } = null!;
+    public DataTemplate MergedAccountMoreExpansionItemTemplate { get; set; } = null!;
+    public DataTemplate FolderMenuTemplate { get; set; } = null!;
+    public DataTemplate SettingsItemTemplate { get; set; } = null!;
+    public DataTemplate MoreItemsFolderTemplate { get; set; } = null!;
+    public DataTemplate RatingItemTemplate { get; set; } = null!;
+    public DataTemplate CreateNewFolderTemplate { get; set; } = null!;
+    public DataTemplate SeperatorTemplate { get; set; } = null!;
+    public DataTemplate NewMailTemplate { get; set; } = null!;
+    public DataTemplate CategoryItemsTemplate { get; set; } = null!;
+    public DataTemplate FixAuthenticationIssueTemplate { get; set; } = null!;
+    public DataTemplate FixMissingFolderConfigTemplate { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item)
     {
@@ -34,7 +34,7 @@ public partial class NavigationMenuTemplateSelector : DataTemplateSelector
             return SettingsItemTemplate;
         else if (item is SeperatorItem)
             return SeperatorTemplate;
-        else if (item is AccountMenuItem accountMenuItem)
+        else if (item is AccountMenuItem)
             // Merged inbox account menu items must be nested.
             return ClickableAccountMenuTemplate;
         else if (item is ManageAccountsMenuItem)
@@ -52,10 +52,6 @@ public partial class NavigationMenuTemplateSelector : DataTemplateSelector
         else if (item is FixAccountIssuesMenuItem fixAccountIssuesMenuItem)
             return fixAccountIssuesMenuItem.Account.AttentionReason == Wino.Core.Domain.Enums.AccountAttentionReason.MissingSystemFolderConfiguration
                     ? FixMissingFolderConfigTemplate : FixAuthenticationIssueTemplate;
-        else
-        {
-            var type = item.GetType();
-            return null;
-        }
+        return MenuItemTemplate;
     }
 }

Wino.Mail.WinUI/Selectors/RsvpStatusIconTemplateSelector.cs

@@ -6,10 +6,10 @@ namespace Wino.Mail.WinUI.Selectors;
 
 public partial class RsvpStatusIconTemplateSelector : DataTemplateSelector
 {
-    public DataTemplate NotRespondedTemplate { get; set; }
-    public DataTemplate ConfirmedTemplate { get; set; }
-    public DataTemplate TentativeTemplate { get; set; }
-    public DataTemplate CancelledTemplate { get; set; }
+    public DataTemplate NotRespondedTemplate { get; set; } = null!;
+    public DataTemplate ConfirmedTemplate { get; set; } = null!;
+    public DataTemplate TentativeTemplate { get; set; } = null!;
+    public DataTemplate CancelledTemplate { get; set; } = null!;
 
     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
     {
@@ -25,6 +25,6 @@ public partial class RsvpStatusIconTemplateSelector : DataTemplateSelector
             };
         }
         
-        return base.SelectTemplateCore(item, container);
+        return base.SelectTemplateCore(item, container) ?? NotRespondedTemplate;
     }
 }

Wino.Mail.WinUI/Selectors/WinoCalendarItemTemplateSelector.cs

@@ -8,8 +8,8 @@ public partial class WinoCalendarItemTemplateSelector : DataTemplateSelector
 {
     public CalendarDisplayType DisplayType { get; set; }
 
-    public DataTemplate DayWeekWorkWeekTemplate { get; set; }
-    public DataTemplate MonthlyTemplate { get; set; }
+    public DataTemplate DayWeekWorkWeekTemplate { get; set; } = null!;
+    public DataTemplate MonthlyTemplate { get; set; } = null!;
 
 
     protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
@@ -26,6 +26,6 @@ public partial class WinoCalendarItemTemplateSelector : DataTemplateSelector
                 break;
         }
 
-        return base.SelectTemplateCore(item, container);
+        return base.SelectTemplateCore(item, container) ?? DayWeekWorkWeekTemplate;
     }
 }

Wino.Mail.WinUI/Services/ApplicationResourceManager.cs

@@ -16,7 +16,7 @@ public class ApplicationResourceManager : IApplicationResourceManager<ResourceDi
         => WinoApplication.Current.Resources.ContainsKey(resourceKey);
 
     public ResourceDictionary GetLastResource()
-        => WinoApplication.Current.Resources.MergedDictionaries.LastOrDefault();
+        => WinoApplication.Current.Resources.MergedDictionaries.LastOrDefault()!;
 
     public void ReplaceResource(string resourceKey, object resource)
         => WinoApplication.Current.Resources[resourceKey] = resource;

Wino.Mail.WinUI/Services/ConfigurationService.cs

@@ -9,10 +9,10 @@ namespace Wino.Mail.WinUI.Services;
 
 public class ConfigurationService : IConfigurationService
 {
-    public T Get<T>(string key, T defaultValue = default)
+    public T Get<T>(string key, T defaultValue = default!)
         => GetInternal(key, ApplicationData.Current.LocalSettings.Values, defaultValue);
 
-    public T GetRoaming<T>(string key, T defaultValue = default)
+    public T GetRoaming<T>(string key, T defaultValue = default!)
         => GetInternal(key, ApplicationData.Current.RoamingSettings.Values, defaultValue);
 
     public void Set(string key, object value)
@@ -21,11 +21,13 @@ public class ConfigurationService : IConfigurationService
     public void SetRoaming(string key, object value)
         => SetInternal(key, value, ApplicationData.Current.RoamingSettings.Values);
 
-    private static T GetInternal<T>(string key, IPropertySet collection, T defaultValue = default)
+    private static T GetInternal<T>(string key, IPropertySet collection, T defaultValue = default!)
     {
-        if (collection.TryGetValue(key, out object value))
+        if (collection.TryGetValue(key, out object? value))
         {
             var stringValue = value?.ToString();
+            if (string.IsNullOrWhiteSpace(stringValue))
+                return defaultValue;
 
             if (typeof(T).IsEnum)
                 return (T)Enum.Parse(typeof(T), stringValue);
@@ -40,7 +42,8 @@ public class ConfigurationService : IConfigurationService
                 return (T)(object)TimeSpan.Parse(stringValue);
             }
 
-            return (T)Convert.ChangeType(stringValue, typeof(T));
+            var converted = Convert.ChangeType(stringValue, typeof(T));
+            return converted is T typed ? typed : defaultValue;
         }
 
         return defaultValue;

Wino.Mail.WinUI/Services/DialogService.cs

@@ -119,7 +119,7 @@ public class DialogService : DialogServiceBase, IMailDialogService
 
         await HandleDialogPresentationAsync(accountPicker);
 
-        return accountPicker.PickedAccount;
+        return accountPicker.PickedAccount ?? null!;
     }
 
     public async Task<AccountSignature> ShowSignatureEditorDialog(AccountSignature? signatureModel = null)

Wino.Mail.WinUI/Services/DialogServiceBase.cs

@@ -40,7 +40,7 @@ public class DialogServiceBase : IDialogServiceBase
         ApplicationResourceManager = applicationResourceManager;
     }
 
-    protected XamlRoot GetXamlRoot()
+    protected XamlRoot? GetXamlRoot()
     {
         return WinoApplication.MainWindow?.Content?.XamlRoot;
     }
@@ -54,7 +54,10 @@ public class DialogServiceBase : IDialogServiceBase
 
         picker.FileTypeFilter.Add("*");
 
-        nint windowHandle = WindowNative.GetWindowHandle(WinoApplication.MainWindow);
+        var mainWindow = WinoApplication.MainWindow;
+        if (mainWindow == null) return string.Empty;
+
+        nint windowHandle = WindowNative.GetWindowHandle(mainWindow);
         InitializeWithWindow.Initialize(picker, windowHandle);
 
         var folder = await picker.PickSingleFolderAsync();
@@ -94,7 +97,10 @@ public class DialogServiceBase : IDialogServiceBase
             picker.FileTypeFilter.Add(filter.ToString());
         }
 
-        nint windowHandle = WindowNative.GetWindowHandle(WinoApplication.MainWindow);
+        var mainWindow = WinoApplication.MainWindow;
+        if (mainWindow == null) return returnList;
+
+        nint windowHandle = WindowNative.GetWindowHandle(mainWindow);
         InitializeWithWindow.Initialize(picker, windowHandle);
 
         var files = await picker.PickMultipleFilesAsync();
@@ -111,7 +117,7 @@ public class DialogServiceBase : IDialogServiceBase
         return returnList;
     }
 
-    private async Task<StorageFile> PickFileAsync(params object[] typeFilters)
+    private async Task<StorageFile?> PickFileAsync(params object[] typeFilters)
     {
         var picker = new FileOpenPicker
         {
@@ -123,7 +129,10 @@ public class DialogServiceBase : IDialogServiceBase
             picker.FileTypeFilter.Add(filter.ToString());
         }
 
-        nint windowHandle = WindowNative.GetWindowHandle(WinoApplication.MainWindow);
+        var mainWindow = WinoApplication.MainWindow;
+        if (mainWindow == null) return null;
+
+        nint windowHandle = WindowNative.GetWindowHandle(mainWindow);
         InitializeWithWindow.Initialize(picker, windowHandle);
 
         var file = await picker.PickSingleFileAsync();
@@ -174,7 +183,7 @@ public class DialogServiceBase : IDialogServiceBase
 
         if (isDontAskEnabled && ConfigurationService.Get(dontAskAgainConfigurationKey, false)) return false;
 
-        var informationContainer = new CustomMessageDialogInformationContainer(title, description, icon.Value, isDontAskEnabled);
+        var informationContainer = new CustomMessageDialogInformationContainer(title, description, icon ?? WinoCustomMessageDialogIcon.Information, isDontAskEnabled);
 
         var dialog = new ContentDialog
         {
@@ -270,7 +279,10 @@ public class DialogServiceBase : IDialogServiceBase
 
         picker.FileTypeFilter.Add("*");
 
-        nint windowHandle = WindowNative.GetWindowHandle(WinoApplication.MainWindow);
+        var mainWindow = WinoApplication.MainWindow;
+        if (mainWindow == null) return string.Empty;
+
+        nint windowHandle = WindowNative.GetWindowHandle(mainWindow);
         InitializeWithWindow.Initialize(picker, windowHandle);
 
         var pickedFolder = await picker.PickSingleFolderAsync();
@@ -307,10 +319,10 @@ public class DialogServiceBase : IDialogServiceBase
 
         await HandleDialogPresentationAsync(dialog);
 
-        return dialog.Result;
+        return dialog.Result ?? null!;
     }
 
-    public async Task<WebView2PrintSettingsModel> ShowPrintDialogAsync(WebView2PrintSettingsModel initialSettings = null)
+    public async Task<WebView2PrintSettingsModel> ShowPrintDialogAsync(WebView2PrintSettingsModel initialSettings = default!)
     {
         try
         {
@@ -334,13 +346,13 @@ public class DialogServiceBase : IDialogServiceBase
             // Return the settings if user clicked Print, otherwise null
             return result == ContentDialogResult.Primary
                 ? dialog.PrintSettings
-                : null;
+                : null!;
         }
         catch (Exception ex)
         {
             // Log the exception if logging is available
             Log.Error(ex, "Error showing print dialog");
-            return null;
+            return null!;
         }
     }
 }

Wino.Mail.WinUI/Services/NativeAppService.cs

@@ -16,10 +16,10 @@ namespace Wino.Services;
 
 public class NativeAppService : INativeAppService
 {
-    private string _mimeMessagesFolder;
-    private string _editorBundlePath;
+    private string _mimeMessagesFolder = string.Empty;
+    private string _editorBundlePath = string.Empty;
 
-    public Func<IntPtr> GetCoreWindowHwnd { get; set; }
+    public Func<IntPtr> GetCoreWindowHwnd { get; set; } = static () => IntPtr.Zero;
 
     public string GetWebAuthenticationBrokerUri()
     {

Wino.Mail.WinUI/Services/NavigationService.cs

@@ -100,7 +100,10 @@ public class NavigationService : NavigationServiceBase, INavigationService
 
         if (frameType == NavigationReferenceFrame.ShellFrame) return shellWindow.GetMainFrame();
 
-        return WinoVisualTreeHelper.GetChildObject<Frame>(mainFrame.Content as UIElement, frameType.ToString());
+        var contentRoot = mainFrame.Content as UIElement;
+        if (contentRoot == null) return mainFrame;
+
+        return WinoVisualTreeHelper.GetChildObject<Frame>(contentRoot, frameType.ToString()) ?? mainFrame;
     }
 
     public bool ChangeApplicationMode(WinoApplicationMode mode)

Wino.Mail.WinUI/Services/NavigationServiceBase.cs

@@ -17,7 +17,7 @@ public class NavigationServiceBase
         };
     }
 
-    public Type GetCurrentFrameType(ref Frame _frame)
+    public Type? GetCurrentFrameType(ref Frame _frame)
     {
         if (_frame != null && _frame.Content != null)
             return _frame.Content.GetType();

Wino.Mail.WinUI/Services/NewThemeService.cs

@@ -45,9 +45,9 @@ public class NewThemeService : INewThemeService
     private static string _snowflakeThemeId = "e143ddde-2e28-4846-9d98-dad63d6505f1";
     private static string _gardenThemeId = "698e4466-f88c-4799-9c61-f0ea1308ed49";
 
-    public event EventHandler<ApplicationElementTheme> ElementThemeChanged;
-    public event EventHandler<string> AccentColorChanged;
-    public event EventHandler<WindowBackdropType> BackdropChanged;
+    public event EventHandler<ApplicationElementTheme>? ElementThemeChanged;
+    public event EventHandler<string>? AccentColorChanged;
+    public event EventHandler<WindowBackdropType>? BackdropChanged;
 
     private const string AccentColorKey = nameof(AccentColorKey);
     private const string CurrentApplicationThemeKey = nameof(CurrentApplicationThemeKey);
@@ -125,7 +125,7 @@ public class NewThemeService : INewThemeService
         }
     }
 
-    private string accentColor;
+    private string accentColor = string.Empty;
 
     public string AccentColor
     {
@@ -218,7 +218,7 @@ public class NewThemeService : INewThemeService
 
         try
         {
-            Microsoft.UI.Xaml.Media.SystemBackdrop backdrop = backdropType switch
+            Microsoft.UI.Xaml.Media.SystemBackdrop? backdrop = backdropType switch
             {
                 WindowBackdropType.Mica => new MicaBackdrop() { Kind = Microsoft.UI.Composition.SystemBackdrops.MicaKind.Base },
                 WindowBackdropType.MicaAlt => new MicaBackdrop() { Kind = Microsoft.UI.Composition.SystemBackdrops.MicaKind.BaseAlt },
@@ -385,7 +385,7 @@ public class NewThemeService : INewThemeService
             return;
         }
 
-        AppThemeBase applyingTheme = null;
+        AppThemeBase? applyingTheme = null;
 
         var controlThemeList = new List<AppThemeBase>(preDefinedThemes);
 
@@ -416,13 +416,19 @@ public class NewThemeService : INewThemeService
             }
         }
 
+        if (applyingTheme == null)
+        {
+            Debug.WriteLine($"Theme with ID {currentApplicationThemeId} not found, skipping theme application");
+            return;
+        }
+
         try
         {
             var existingThemeDictionary = _applicationResourceManager.GetLastResource();
 
-            if (existingThemeDictionary != null && existingThemeDictionary.TryGetValue("ThemeName", out object themeNameString))
+            if (existingThemeDictionary != null && existingThemeDictionary.TryGetValue("ThemeName", out object? themeNameString))
             {
-                var themeName = themeNameString.ToString();
+                var themeName = themeNameString?.ToString();
 
                 // Applying different theme.
                 if (themeName != applyingTheme.ThemeName)
@@ -430,6 +436,10 @@ public class NewThemeService : INewThemeService
                     var resourceDictionaryContent = await applyingTheme.GetThemeResourceDictionaryContentAsync();
 
                     var resourceDictionary = XamlReader.Load(resourceDictionaryContent) as ResourceDictionary;
+                    if (resourceDictionary == null)
+                    {
+                        return;
+                    }
 
                     // Custom themes require special attention for background image because 
                     // they share the same base theme resource dictionary.
@@ -561,7 +571,7 @@ public class NewThemeService : INewThemeService
         return results;
     }
 
-    private async Task<CustomThemeMetadata> GetCustomMetadataAsync(IStorageFile file)
+    private async Task<CustomThemeMetadata?> GetCustomMetadataAsync(IStorageFile file)
     {
         var fileContent = await FileIO.ReadTextAsync(file);
 

Wino.Mail.WinUI/Services/NotificationBuilder.cs

@@ -215,7 +215,12 @@ public class NotificationBuilder : INotificationBuilder
                 XmlDocument badgeXml = BadgeUpdateManager.GetTemplateContent(BadgeTemplateType.BadgeNumber);
 
                 // Set the value of the badge in the XML to our number
-                XmlElement badgeElement = badgeXml.SelectSingleNode("/badge") as XmlElement;
+                XmlElement? badgeElement = badgeXml.SelectSingleNode("/badge") as XmlElement;
+                if (badgeElement == null)
+                {
+                    badgeUpdater.Clear();
+                    return;
+                }
                 badgeElement.SetAttribute("value", totalUnreadCount.ToString());
 
                 // Create the badge notification

Wino.Mail.WinUI/Services/PreferencesService.cs

@@ -17,20 +17,20 @@ public class PreferencesService(IConfigurationService configurationService) : Ob
 {
     private readonly IConfigurationService _configurationService = configurationService;
 
-    public event EventHandler<string> PreferenceChanged;
+    public event EventHandler<string>? PreferenceChanged;
 
     protected override void OnPropertyChanged(PropertyChangedEventArgs e)
     {
         base.OnPropertyChanged(e);
 
-        PreferenceChanged?.Invoke(this, e.PropertyName);
+        PreferenceChanged?.Invoke(this, e.PropertyName ?? string.Empty);
     }
 
-    private void SaveProperty(string propertyName, object value) => _configurationService.Set(propertyName, value);
+    private void SaveProperty(string propertyName, object? value) => _configurationService.Set(propertyName, value ?? string.Empty);
 
-    private void SetPropertyAndSave(string propertyName, object value)
+    private void SetPropertyAndSave(string propertyName, object? value)
     {
-        _configurationService.Set(propertyName, value);
+        _configurationService.Set(propertyName, value ?? string.Empty);
 
         OnPropertyChanged(propertyName);
         Debug.WriteLine($"PreferencesService -> {propertyName}:{value?.ToString()}");

Wino.Mail.WinUI/Services/PrintService.cs

@@ -24,10 +24,10 @@ namespace Wino.Mail.WinUI.Services;
 
 public class PrintService : IPrintService
 {
-    private TaskCompletionSource<PrintingResult> _taskCompletionSource;
-    private CanvasPrintDocument printDocument;
-    private PrintTask printTask;
-    private PdfDocument pdfDocument;
+    private TaskCompletionSource<PrintingResult>? _taskCompletionSource;
+    private CanvasPrintDocument? printDocument;
+    private PrintTask? printTask;
+    private PdfDocument? pdfDocument;
 
     private List<CanvasBitmap> bitmaps = new();
     private Vector2 largestBitmap;
@@ -41,7 +41,7 @@ public class PrintService : IPrintService
     private int bitmapsPerPage;
     private int pageCount = -1;
 
-    private PrintInformation _currentPrintInformation;
+    private PrintInformation? _currentPrintInformation;
 
     public async Task<PrintingResult> PrintPdfFileAsync(string pdfFilePath, string printTitle)
     {
@@ -125,6 +125,9 @@ public class PrintService : IPrintService
 
         printTask = args.Request.CreatePrintTask(_currentPrintInformation.PDFTitle, (createPrintTaskArgs) =>
         {
+            if (printDocument == null)
+                return;
+
             createPrintTaskArgs.SetSource(printDocument);
         });
 
@@ -191,6 +194,9 @@ public class PrintService : IPrintService
 
     private async Task LoadPDFPageBitmapsAsync(CanvasPrintDocument sender)
     {
+        if (pdfDocument == null)
+            return;
+
         ClearBitmaps();
 
         bitmaps ??= new List<CanvasBitmap>();
@@ -226,6 +232,9 @@ public class PrintService : IPrintService
     {
         var detailedOptions = PrintTaskOptionDetails.GetFromPrintTaskOptions(args.PrintTaskOptions);
 
+        if (pdfDocument == null)
+            return;
+
         int pageCountToPrint = (int)pdfDocument.PageCount;
 
         for (uint i = 1; i <= pageCountToPrint; ++i)
@@ -239,7 +248,7 @@ public class PrintService : IPrintService
 
     private void DrawPdfPage(CanvasPrintDocument sender, CanvasDrawingSession ds, uint pageNumber)
     {
-        if (bitmaps?.Count == 0) return;
+        if (bitmaps.Count == 0) return;
 
         var cellAcross = new Vector2(cellSize.X, 0);
         var cellDown = new Vector2(0, cellSize.Y);

Wino.Mail.WinUI/Services/SmimeCertificateService.cs

@@ -17,7 +17,7 @@ public class SmimeCertificateService : ISmimeCertificateService
     /// private key and at least one extension. The store is opened in read-only mode.</remarks>
     /// <returns>An enumerable collection of <see cref="X509Certificate2"/> objects representing the personal certificates that
     /// meet the specified criteria. If no matching certificates are found, the collection will be empty.</returns>
-    public IEnumerable<X509Certificate2> GetCertificates(StoreName storeName = StoreName.My, StoreLocation storeLocation = StoreLocation.CurrentUser, string emailAddress = null)
+    public IEnumerable<X509Certificate2> GetCertificates(StoreName storeName = StoreName.My, StoreLocation storeLocation = StoreLocation.CurrentUser, string? emailAddress = null)
     {
         using var store = new X509Store(storeName, storeLocation);
         store.Open(OpenFlags.ReadOnly);
@@ -26,7 +26,7 @@ public class SmimeCertificateService : ISmimeCertificateService
     }
 
 
-    public void ImportCertificate(string fileExtension, byte[] rawData, string password = null, StoreName storeName = StoreName.My, StoreLocation storeLocation = StoreLocation.CurrentUser)
+    public void ImportCertificate(string fileExtension, byte[] rawData, string? password = null, StoreName storeName = StoreName.My, StoreLocation storeLocation = StoreLocation.CurrentUser)
     {
         X509Certificate2Collection collection = [];
 

Wino.Mail.WinUI/Services/StatePersistenceService.cs

@@ -198,7 +198,13 @@ public class StatePersistenceService : ObservableObject, IStatePersistanceServic
         }
     }
 
-    private void UpdateAppCoreWindowTitle() => WinoApplication.MainWindow.Title = CoreWindowTitle;
+    private void UpdateAppCoreWindowTitle()
+    {
+        if (WinoApplication.MainWindow != null)
+        {
+            WinoApplication.MainWindow.Title = CoreWindowTitle;
+        }
+    }
 
     private static CalendarDisplayType EnsureValidCalendarDisplayType(CalendarDisplayType displayType)
     {

Wino.Mail.WinUI/Services/ThumbnailService.cs

@@ -21,7 +21,7 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
     private static readonly HttpClient _httpClient = new();
     private bool _isInitialized = false;
 
-    private ConcurrentDictionary<string, (string graviton, string favicon)> _cache;
+    private ConcurrentDictionary<string, (string? graviton, string? favicon)> _cache = [];
     private readonly ConcurrentDictionary<string, Task> _requests = [];
 
     private static readonly List<string> _excludedFaviconDomains = [
@@ -43,7 +43,7 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
         "rediffmail.com"
         ];
 
-    public async ValueTask<string> GetThumbnailAsync(string email, bool awaitLoad = false)
+    public async ValueTask<string?> GetThumbnailAsync(string email, bool awaitLoad = false)
     {
         if (string.IsNullOrWhiteSpace(email))
             return null;
@@ -55,8 +55,8 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
         {
             var thumbnailsList = await _databaseService.Connection.Table<Thumbnail>().ToListAsync();
 
-            _cache = new ConcurrentDictionary<string, (string graviton, string favicon)>(
-                thumbnailsList.ToDictionary(x => x.Domain, x => (x.Gravatar, x.Favicon)));
+            _cache = new ConcurrentDictionary<string, (string? graviton, string? favicon)>(
+                thumbnailsList.ToDictionary(x => x.Domain, x => ((string?)x.Gravatar, (string?)x.Favicon)));
             _isInitialized = true;
         }
 
@@ -84,7 +84,7 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
         await _databaseService.Connection.DeleteAllAsync<Thumbnail>();
     }
 
-    private async ValueTask<(string gravatar, string favicon)> GetThumbnailInternal(string email, bool awaitLoad)
+    private async ValueTask<(string? gravatar, string? favicon)> GetThumbnailInternal(string email, bool awaitLoad)
     {
         if (_cache.TryGetValue(email, out var cached))
             return cached;
@@ -136,7 +136,7 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
         WeakReferenceMessenger.Default.Send(new ThumbnailAdded(email));
     }
 
-    private static async Task<string> GetGravatarBase64(string email)
+    private static async Task<string?> GetGravatarBase64(string email)
     {
         try
         {
@@ -156,7 +156,7 @@ public class ThumbnailService(IPreferencesService preferencesService, IDatabaseS
         return null;
     }
 
-    private static async Task<string> GetFaviconBase64(string email)
+    private static async Task<string?> GetFaviconBase64(string email)
     {
         try
         {

Wino.Mail.WinUI/Views/Calendar/CalendarPage.xaml.cs

@@ -26,7 +26,7 @@ public sealed partial class CalendarPage : CalendarPageAbstract,
         ViewModel.DetailsShowCalendarItemChanged += CalendarItemDetailContextChanged;
     }
 
-    private void CalendarItemDetailContextChanged(object sender, EventArgs e)
+    private void CalendarItemDetailContextChanged(object? sender, EventArgs e)
     {
         if (ViewModel.DisplayDetailsCalendarItemViewModel != null)
         {

Wino.Mail.WinUI/Views/Settings/AliasManagementPage.xaml.cs

@@ -37,7 +37,7 @@ public sealed partial class AliasManagementPage : AliasManagementPageAbstract
         }
     }
 
-    private static (MailAccountAlias alias, X509Certificate2 cert) GetAliasAndSelectedCertificateForCombobox(object sender)
+    private static (MailAccountAlias? alias, X509Certificate2? cert) GetAliasAndSelectedCertificateForCombobox(object sender)
     {
         var comboBox = sender as ComboBox;
         var alias = comboBox?.DataContext as MailAccountAlias;

Wino.Mail.WinUI/Views/Settings/ContactsPage.xaml.cs

@@ -89,7 +89,7 @@ public sealed partial class ContactsPage : ContactsPageAbstract
         ClearSelection();
     }
 
-    private void ViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
+    private void ViewModelPropertyChanged(object? sender, PropertyChangedEventArgs e)
     {
         if (e.PropertyName == nameof(ContactsPageViewModel.IsSelectionMode) && !ViewModel.IsSelectionMode)
         {

Wino.Mail.WinUI/Wino.Mail.WinUI.csproj

@@ -5,6 +5,7 @@
     <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
     <RootNamespace>Wino.Mail.WinUI</RootNamespace>
     <ApplicationManifest>app.manifest</ApplicationManifest>
+    <Platform Condition="'$(Platform)' == '' or '$(Platform)' == 'AnyCPU'">x64</Platform>
     <Platforms>x86;x64;ARM64</Platforms>
     <RuntimeIdentifiers>win-x86;win-x64;win-arm64</RuntimeIdentifiers>
     <PublishProfile>win-$(Platform).pubxml</PublishProfile>
@@ -15,7 +16,8 @@
 	<!-- AOT / Trimming -->
 	<PublishAot Condition="'$(Configuration)' == 'Debug'">False</PublishAot>
 	<PublishAot Condition="'$(Configuration)' != 'Debug'">True</PublishAot>
-	<TreatWarningsAsErrors>False</TreatWarningsAsErrors>
+	<TreatWarningsAsErrors>True</TreatWarningsAsErrors>
+	<NoWarn>$(NoWarn);CS8305</NoWarn>
 	<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
 	<PublishReadyToRun Condition="'$(Configuration)' == 'Debug'">False</PublishReadyToRun>
 	<PublishReadyToRun Condition="'$(Configuration)' != 'Debug'">True</PublishReadyToRun>

Wino.Mail.WinUI/WinoApplication.cs

@@ -38,7 +38,7 @@ public abstract class WinoApplication : Application, IRecipient<LanguageChanged>
     protected IDatabaseService DatabaseService { get; }
     protected ITranslationService TranslationService { get; }
 
-    public static WindowEx MainWindow { get; set; }
+    public static WindowEx? MainWindow { get; set; }
 
     protected WinoApplication()
     {
@@ -50,14 +50,14 @@ public abstract class WinoApplication : Application, IRecipient<LanguageChanged>
         TaskScheduler.UnobservedTaskException += OnUnobservedTaskException;
         UnhandledException += OnAppUnhandledException;
 
-        LogInitializer = Services.GetService<IWinoLogger>();
-        AppConfiguration = Services.GetService<IApplicationConfiguration>();
+        LogInitializer = Services.GetRequiredService<IWinoLogger>();
+        AppConfiguration = Services.GetRequiredService<IApplicationConfiguration>();
 
-        NewThemeService = Services.GetService<INewThemeService>();
-        DatabaseService = Services.GetService<IDatabaseService>();
-        TranslationService = Services.GetService<ITranslationService>();
-        UnderlyingThemeService = Services.GetService<IUnderlyingThemeService>();
-        ThumbnailService = Services.GetService<IThumbnailService>();
+        NewThemeService = Services.GetRequiredService<INewThemeService>();
+        DatabaseService = Services.GetRequiredService<IDatabaseService>();
+        TranslationService = Services.GetRequiredService<ITranslationService>();
+        UnderlyingThemeService = Services.GetRequiredService<IUnderlyingThemeService>();
+        ThumbnailService = Services.GetRequiredService<IThumbnailService>();
 
         // Make sure the paths are setup on app start.
         AppConfiguration.ApplicationDataFolderPath = ApplicationData.Current.LocalFolder.Path;
@@ -67,10 +67,10 @@ public abstract class WinoApplication : Application, IRecipient<LanguageChanged>
         ConfigureLogging();
     }
 
-    private void CurrentDomain_UnhandledException(object sender, System.UnhandledExceptionEventArgs e)
+    private void CurrentDomain_UnhandledException(object? sender, System.UnhandledExceptionEventArgs e)
         => Log.Fatal(e.ExceptionObject as Exception, "AppDomain Unhandled Exception");
 
-    private void OnUnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
+    private void OnUnobservedTaskException(object? sender, UnobservedTaskExceptionEventArgs e)
         => Log.Error(e.Exception, "Unobserved Task Exception");
 
     private void OnAppUnhandledException(object sender, Microsoft.UI.Xaml.UnhandledExceptionEventArgs e)
@@ -83,7 +83,7 @@ public abstract class WinoApplication : Application, IRecipient<LanguageChanged>
     {
         yield return DatabaseService;
         yield return TranslationService;
-        yield return Services.GetService<SynchronizationManagerInitializer>();
+        yield return Services.GetRequiredService<SynchronizationManagerInitializer>();
     }
 
     public Task InitializeServicesAsync() => GetActivationServices().Select(a => a.InitializeAsync()).WhenAll();

Wino.SourceGenerators/Translator/TranslatorGenerator.cs

@@ -43,7 +43,7 @@ namespace Wino.Core.SourceGeneration.Translator
 
         // Get the JSON schema and track changes
         var jsonSchema = context.AdditionalTextsProvider
-            .Where(static file => file.Path.EndsWith("en_US\\resources.json"))
+            .Where(static file => file.Path.Replace("\\", "/").EndsWith("en_US/resources.json", StringComparison.OrdinalIgnoreCase))
             .Select((text, _) => (text, text.GetText()))
             .Collect()
             .WithTrackingName("JsonSchema");

Wino.SourceGenerators/Wino.SourceGenerators.csproj

@@ -3,6 +3,7 @@
 	<PropertyGroup>
 		<TargetFramework>netstandard2.0</TargetFramework>
 		<Nullable>enable</Nullable>
+		<LangVersion>latest</LangVersion>
 		<IncludeBuildOutput>false</IncludeBuildOutput>
 		<PlatformTarget>AnyCPU</PlatformTarget>
 		<EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>