Nullability annotations for Avalonia.Win32

src/Avalonia.Base/Platform/IPlatformThreadingInterface.cs

@@ -26,6 +26,6 @@ namespace Avalonia.Platform
 
         bool CurrentThreadIsLoopThread { get; }
 
-        event Action<DispatcherPriority?> Signaled;
+        event Action<DispatcherPriority?>? Signaled;
     }
 }

src/Avalonia.Base/Platform/Storage/FilePickerFileType.cs

@@ -7,9 +7,9 @@ namespace Avalonia.Platform.Storage;
 /// </summary>
 public sealed class FilePickerFileType
 {
-    public FilePickerFileType(string name)
+    public FilePickerFileType(string? name)
     {
-        Name = name;
+        Name = name ?? string.Empty;
     }
 
     /// <summary>

src/Avalonia.Base/Rendering/IRenderTimer.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Threading.Tasks;
 using Avalonia.Metadata;
 
 namespace Avalonia.Rendering

src/Avalonia.Controls/Platform/IPlatformLifetimeEventsImpl.cs

@@ -13,6 +13,6 @@ namespace Avalonia.Platform
         /// <remarks>
         /// Raised on on OSX via the Quit menu or right-clicking on the application icon and selecting Quit.
         /// </remarks>
-        event EventHandler<ShutdownRequestedEventArgs> ShutdownRequested;
+        event EventHandler<ShutdownRequestedEventArgs>? ShutdownRequested;
     }
 }

src/Avalonia.Controls/Platform/IWindowImpl.cs

@@ -19,7 +19,7 @@ namespace Avalonia.Platform
         /// <summary>
         /// Gets or sets a method called when the minimized/maximized state of the window changes.
         /// </summary>
-        Action<WindowState> WindowStateChanged { get; set; }
+        Action<WindowState>? WindowStateChanged { get; set; }
 
         /// <summary>
         /// Sets the title of the window.
@@ -42,7 +42,7 @@ namespace Avalonia.Platform
         /// <summary>
         /// Called when a disabled window received input. Can be used to activate child windows.
         /// </summary>
-        Action GotInputWhenDisabled { get; set; }        
+        Action? GotInputWhenDisabled { get; set; }
 
         /// <summary>
         /// Enables or disables system window decorations (title bar, buttons, etc)
@@ -68,7 +68,7 @@ namespace Avalonia.Platform
         /// Gets or sets a method called before the underlying implementation is destroyed.
         /// Return true to prevent the underlying implementation from closing.
         /// </summary>
-        Func<WindowCloseReason, bool> Closing { get; set; }
+        Func<WindowCloseReason, bool>? Closing { get; set; }
 
         /// <summary>
         /// Gets a value to indicate if the platform was able to extend client area to non-client area.
@@ -78,7 +78,7 @@ namespace Avalonia.Platform
         /// <summary>
         /// Gets or Sets an action that is called whenever one of the extend client area properties changed.
         /// </summary>
-        Action<bool> ExtendClientAreaToDecorationsChanged { get; set; }
+        Action<bool>? ExtendClientAreaToDecorationsChanged { get; set; }
 
         /// <summary>
         /// Gets a flag that indicates if Managed decorations i.e. caption buttons are required.

src/Avalonia.Controls/WindowBase.cs

@@ -94,7 +94,7 @@ namespace Avalonia.Controls
             private set { SetAndRaise(IsActiveProperty, ref _isActive, value); }
         }
         
-        public Screens Screens { get; private set; }
+        public Screens Screens { get; }
 
         /// <summary>
         /// Gets or sets the owner of the window.

src/Windows/Avalonia.Win32/AngleOptions.cs

@@ -17,6 +17,6 @@ namespace Avalonia.Win32
             new GlVersion(GlProfileType.OpenGLES, 2, 0)
         };
 
-        public IList<PlatformApi> AllowedPlatformApis { get; set; } = null;
+        public IList<PlatformApi>? AllowedPlatformApis { get; set; } = null;
     }
 }

src/Windows/Avalonia.Win32/Automation/AutomationNode.ExpandCollapse.cs

@@ -2,8 +2,6 @@
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.IExpandCollapseProvider

src/Windows/Avalonia.Win32/Automation/AutomationNode.RangeValue.cs

@@ -1,8 +1,6 @@
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.IRangeValueProvider

src/Windows/Avalonia.Win32/Automation/AutomationNode.Scroll.cs

@@ -1,8 +1,6 @@
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.IScrollProvider, UIA.IScrollItemProvider

src/Windows/Avalonia.Win32/Automation/AutomationNode.Selection.cs

@@ -1,12 +1,9 @@
-using System;
+using System.Collections.Generic;
-using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Automation.Peers;
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.ISelectionProvider, UIA.ISelectionItemProvider
@@ -27,8 +24,7 @@ namespace Avalonia.Win32.Automation
         UIA.IRawElementProviderSimple[] UIA.ISelectionProvider.GetSelection()
         {
             var peers = InvokeSync<ISelectionProvider, IReadOnlyList<AutomationPeer>>(x => x.GetSelection());
-            return peers?.Select(x => (UIA.IRawElementProviderSimple)GetOrCreate(x)!).ToArray() ??
+            return peers.Select(x => (UIA.IRawElementProviderSimple)GetOrCreate(x)).ToArray();
-                Array.Empty<UIA.IRawElementProviderSimple>();
         }
 
         void UIA.ISelectionItemProvider.AddToSelection() => InvokeSync<ISelectionItemProvider>(x => x.AddToSelection());

src/Windows/Avalonia.Win32/Automation/AutomationNode.Toggle.cs

@@ -1,8 +1,6 @@
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.IToggleProvider

src/Windows/Avalonia.Win32/Automation/AutomationNode.Value.cs

@@ -2,8 +2,6 @@
 using Avalonia.Automation.Provider;
 using UIA = Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     internal partial class AutomationNode : UIA.IValueProvider

src/Windows/Avalonia.Win32/Automation/AutomationNode.cs

@@ -12,8 +12,6 @@ using Avalonia.Threading;
 using Avalonia.Win32.Interop.Automation;
 using AAP = Avalonia.Automation.Provider;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     [ComVisible(true)]
@@ -25,7 +23,7 @@ namespace Avalonia.Win32.Automation
         IRawElementProviderAdviseEvents,
         IInvokeProvider
     {
-        private static Dictionary<AutomationProperty, UiaPropertyId> s_propertyMap = new Dictionary<AutomationProperty, UiaPropertyId>()
+        private static Dictionary<AutomationProperty, UiaPropertyId> s_propertyMap = new()
         {
             { AutomationElementIdentifiers.BoundingRectangleProperty, UiaPropertyId.BoundingRectangle },
             { AutomationElementIdentifiers.ClassNameProperty, UiaPropertyId.ClassName },
@@ -46,8 +44,7 @@ namespace Avalonia.Win32.Automation
             { SelectionPatternIdentifiers.SelectionProperty, UiaPropertyId.SelectionSelection },
         };
 
-        private static ConditionalWeakTable<AutomationPeer, AutomationNode> s_nodes =
+        private static ConditionalWeakTable<AutomationPeer, AutomationNode> s_nodes = new();
-            new ConditionalWeakTable<AutomationPeer, AutomationNode>();
 
         private readonly int[] _runtimeId;
         private int _raiseFocusChanged;
@@ -174,11 +171,12 @@ namespace Avalonia.Win32.Automation
                     NavigateDirection.LastChild => GetOrCreate(Peer.GetChildren().LastOrDefault()),
                     _ => null,
                 };
-            }) as IRawElementProviderFragment;
+            });
         }
 
         public void SetFocus() => InvokeSync(() => Peer.SetFocus());
 
+        [return: NotNullIfNotNull(nameof(peer))]
         public static AutomationNode? GetOrCreate(AutomationPeer? peer)
         {
             return peer is null ? null : s_nodes.GetValue(peer, Create);

src/Windows/Avalonia.Win32/Automation/RootAutomationNode.cs

@@ -6,8 +6,6 @@ using Avalonia.Automation.Provider;
 using Avalonia.Platform;
 using Avalonia.Win32.Interop.Automation;
 
-#nullable enable
-
 namespace Avalonia.Win32.Automation
 {
     [RequiresUnreferencedCode("Requires .NET COM interop")]

src/Windows/Avalonia.Win32/Avalonia.Win32.csproj

@@ -6,7 +6,6 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
-    <Compile Include="..\..\Avalonia.Base\Metadata\NullableAttributes.cs" Link="NullableAttributes.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\packages\Avalonia\Avalonia.csproj" />
@@ -16,7 +15,8 @@
     <MicroComIdl Include="Win32Com\win32.idl" CSharpInteropPath="Win32Com\Win32.Generated.cs" />
     <MicroComIdl Include="DirectX\directx.idl" CSharpInteropPath="DirectX\directx.Generated.cs" />
   </ItemGroup>
-  <Import Project="$(MSBuildThisFileDirectory)\..\..\..\build\System.Drawing.Common.props" />
+  <Import Project="..\..\..\build\System.Drawing.Common.props" />
+  <Import Project="..\..\..\build\NullableEnable.props" />
   <Import Project="..\..\..\build\DevAnalyzers.props" />
   <Import Project="..\..\..\build\SourceGenerators.props" />
   <ItemGroup>

src/Windows/Avalonia.Win32/ClipboardFormats.cs

@@ -8,15 +8,15 @@ using Avalonia.Utilities;
 
 namespace Avalonia.Win32
 {
-    static class ClipboardFormats
+    internal static class ClipboardFormats
     {
         private const int MAX_FORMAT_NAME_LENGTH = 260;
 
-        class ClipboardFormat
+        private class ClipboardFormat
         {
-            public ushort Format { get; private set; }
+            public ushort Format { get; }
-            public string Name { get; private set; }
+            public string Name { get; }
-            public ushort[] Synthesized { get; private set; }
+            public ushort[] Synthesized { get; }
 
             public ClipboardFormat(string name, ushort format, params ushort[] synthesized)
             {
@@ -26,14 +26,14 @@ namespace Avalonia.Win32
             }
         }
 
-        private static readonly List<ClipboardFormat> FormatList = new List<ClipboardFormat>()
+        private static readonly List<ClipboardFormat> s_formatList = new()
         {
             new ClipboardFormat(DataFormats.Text, (ushort)UnmanagedMethods.ClipboardFormat.CF_UNICODETEXT, (ushort)UnmanagedMethods.ClipboardFormat.CF_TEXT),
             new ClipboardFormat(DataFormats.FileNames, (ushort)UnmanagedMethods.ClipboardFormat.CF_HDROP),
         };
 
 
-        private static string QueryFormatName(ushort format)
+        private static string? QueryFormatName(ushort format)
         {
             var sb = StringBuilderCache.Acquire(MAX_FORMAT_NAME_LENGTH);
             if (UnmanagedMethods.GetClipboardFormatName(format, sb, sb.Capacity) > 0)
@@ -43,16 +43,16 @@ namespace Avalonia.Win32
 
         public static string GetFormat(ushort format)
         {
-            lock (FormatList)
+            lock (s_formatList)
             {
-                var pd = FormatList.FirstOrDefault(f => f.Format == format || Array.IndexOf(f.Synthesized, format) >= 0);
+                var pd = s_formatList.FirstOrDefault(f => f.Format == format || Array.IndexOf(f.Synthesized, format) >= 0);
                 if (pd == null)
                 {
-                    string name = QueryFormatName(format);
+                    string? name = QueryFormatName(format);
                     if (string.IsNullOrEmpty(name))
-                        name = string.Format("Unknown_Format_{0}", format);
+                        name = $"Unknown_Format_{format}";
                     pd = new ClipboardFormat(name, format);
-                    FormatList.Add(pd);
+                    s_formatList.Add(pd);
                 }
                 return pd.Name;
             }
@@ -60,16 +60,16 @@ namespace Avalonia.Win32
 
         public static ushort GetFormat(string format)
         {
-            lock (FormatList)
+            lock (s_formatList)
             {
-                var pd = FormatList.FirstOrDefault(f => StringComparer.OrdinalIgnoreCase.Equals(f.Name, format));
+                var pd = s_formatList.FirstOrDefault(f => StringComparer.OrdinalIgnoreCase.Equals(f.Name, format));
                 if (pd == null)
                 {
                     int id = UnmanagedMethods.RegisterClipboardFormat(format);
                     if (id == 0)
                         throw new Win32Exception();
                     pd = new ClipboardFormat(format, (ushort)id);
-                    FormatList.Add(pd);
+                    s_formatList.Add(pd);
                 }
                 return pd.Format;
             }

src/Windows/Avalonia.Win32/ClipboardImpl.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Win32
             return Disposable.Create(() => UnmanagedMethods.CloseClipboard());
         }
 
-        public async Task<string> GetTextAsync()
+        public async Task<string?> GetTextAsync()
         {
             using(await OpenClipboard())
             {
@@ -52,19 +52,17 @@ namespace Avalonia.Win32
             }
         }
 
-        public async Task SetTextAsync(string text)
+        public async Task SetTextAsync(string? text)
         {
-            if (text == null)
-            {
-                throw new ArgumentNullException(nameof(text));
-            }
-
             using(await OpenClipboard())
             {
                 UnmanagedMethods.EmptyClipboard();
 
-                var hGlobal = Marshal.StringToHGlobalUni(text);
+                if (text is not null)
-                UnmanagedMethods.SetClipboardData(UnmanagedMethods.ClipboardFormat.CF_UNICODETEXT, hGlobal);
+                {
+                    var hGlobal = Marshal.StringToHGlobalUni(text);
+                    UnmanagedMethods.SetClipboardData(UnmanagedMethods.ClipboardFormat.CF_UNICODETEXT, hGlobal);
+                }
             }
         }
 
@@ -121,7 +119,7 @@ namespace Avalonia.Win32
             }
         }
 
-        public async Task<object> GetDataAsync(string format)
+        public async Task<object?> GetDataAsync(string format)
         {
             Dispatcher.UIThread.VerifyAccess();
             var i = OleRetryCount;

src/Windows/Avalonia.Win32/DataObject.cs

@@ -22,9 +22,9 @@ namespace Avalonia.Win32
         // Compatibility with WinForms + WPF...
         internal static readonly byte[] SerializedObjectGUID = new Guid("FD9EA796-3B13-4370-A679-56106BB288FB").ToByteArray();
 
-        class FormatEnumerator : CallbackBase, Win32Com.IEnumFORMATETC
+        private class FormatEnumerator : CallbackBase, Win32Com.IEnumFORMATETC
         {
-            private FORMATETC[] _formats;
+            private readonly FORMATETC[] _formats;
             private uint _current;
 
             private FormatEnumerator(FORMATETC[] formats, uint current)
@@ -105,16 +105,12 @@ namespace Avalonia.Win32
 
         public DataObject(IDataObject wrapped)
         {
-            if (wrapped == null)
+            _wrapped = wrapped switch
             {
-                throw new ArgumentNullException(nameof(wrapped));
+                null => throw new ArgumentNullException(nameof(wrapped)),
-            }
+                DataObject or OleDataObject => throw new ArgumentException($"Cannot wrap a {wrapped.GetType()}"),
-            if (_wrapped is DataObject || _wrapped is OleDataObject)
+                _ => wrapped
-            {
+            };
-                throw new InvalidOperationException();
-            }
-
-            _wrapped = wrapped;
         }
 
         #region IDataObject
@@ -128,17 +124,17 @@ namespace Avalonia.Win32
             return _wrapped.GetDataFormats();
         }
 
-        IEnumerable<string> IDataObject.GetFileNames()
+        IEnumerable<string>? IDataObject.GetFileNames()
         {
             return _wrapped.GetFileNames();
         }
 
-        string IDataObject.GetText()
+        string? IDataObject.GetText()
         {
             return _wrapped.GetText();
         }
 
-        object IDataObject.Get(string dataFormat)
+        object? IDataObject.Get(string dataFormat)
         {
             return _wrapped.Get(dataFormat);
         }
@@ -182,9 +178,6 @@ namespace Avalonia.Win32
             if (_wrapped is Win32Com.IDataObject ole)
                 return ole.GetCanonicalFormatEtc(formatIn);
 
-            var formatOut = new FORMATETC();
-            formatOut.ptd = IntPtr.Zero;
-
             throw new COMException(nameof(UnmanagedMethods.HRESULT.E_NOTIMPL), unchecked((int)UnmanagedMethods.HRESULT.E_NOTIMPL));
         }
 
@@ -264,9 +257,9 @@ namespace Avalonia.Win32
 
         private uint WriteDataToHGlobal(string dataFormat, ref IntPtr hGlobal)
         {
-            object data = _wrapped.Get(dataFormat);
+            object data = _wrapped.Get(dataFormat)!;
             if (dataFormat == DataFormats.Text || data is string)
-                return WriteStringToHGlobal(ref hGlobal, Convert.ToString(data));
+                return WriteStringToHGlobal(ref hGlobal, Convert.ToString(data) ?? string.Empty);
             if (dataFormat == DataFormats.FileNames && data is IEnumerable<string> files)
                 return WriteFileListToHGlobal(ref hGlobal, files);
             if (data is Stream stream)
@@ -286,7 +279,7 @@ namespace Avalonia.Win32
             }
             if (data is IEnumerable<byte> bytes)
             {
-                var byteArr = bytes is byte[] ? (byte[])bytes : bytes.ToArray();
+                var byteArr = bytes as byte[] ?? bytes.ToArray();
                 return WriteBytesToHGlobal(ref hGlobal, byteArr);
             }
             return WriteBytesToHGlobal(ref hGlobal, SerializeObject(data));
@@ -332,7 +325,7 @@ namespace Avalonia.Win32
 
         private static uint WriteFileListToHGlobal(ref IntPtr hGlobal, IEnumerable<string> files)
         {
-            if (!files?.Any() ?? false)
+            if (!files.Any())
                 return unchecked((int)UnmanagedMethods.HRESULT.S_OK);
 
             char[] filesStr = (string.Join("\0", files) + "\0\0").ToCharArray();
@@ -392,7 +385,7 @@ namespace Avalonia.Win32
 
         public void ReleaseWrapped()
         {
-            _wrapped = null;
+            _wrapped = null!;
         }
         #endregion
     }

src/Windows/Avalonia.Win32/DirectX/DirectXStructs.cs

@@ -1,17 +1,10 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-using System.Text;
-using System.Threading.Tasks;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 // ReSharper disable InconsistentNaming
 #pragma warning disable CS0649
 
 namespace Avalonia.Win32.DirectX
 {
-#nullable enable
     public unsafe struct HANDLE
     {
         public readonly void* Value;
@@ -288,5 +281,4 @@ namespace Avalonia.Win32.DirectX
 
         public D3D11_RESOURCE_MISC_FLAG MiscFlags;
     }
-#nullable restore
 }

src/Windows/Avalonia.Win32/DirectX/DxgiConnection.cs

@@ -1,24 +1,14 @@
 using System;
-using System.Collections.Generic;
-using System.ComponentModel;
 using System.Diagnostics;
-using System.Linq;
-using System.Runtime.InteropServices;
-using System.Text;
 using System.Threading.Tasks;
 using Avalonia.Logging;
-using Avalonia.OpenGL.Angle;
-using Avalonia.OpenGL.Egl;
 using Avalonia.Rendering;
-using Avalonia.Win32.OpenGl.Angle;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 using static Avalonia.Win32.DirectX.DirectXUnmanagedMethods;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.DirectX
 {
-#pragma warning disable CA1416 // This should only be reachable on Windows
-#nullable enable
     public unsafe class DxgiConnection : IRenderTimer
     {
         public const uint ENUM_CURRENT_SETTINGS = unchecked((uint)(-1));
@@ -26,11 +16,11 @@ namespace Avalonia.Win32.DirectX
         public bool RunsInBackground => true;
 
         public event Action<TimeSpan>? Tick;
-        private object _syncLock;
+        private readonly object _syncLock;
 
-        private IDXGIOutput? _output = null;
+        private IDXGIOutput? _output;
 
-        private Stopwatch? _stopwatch = null;
+        private Stopwatch? _stopwatch;
         private const string LogArea = "DXGI";
 
         public DxgiConnection(object syncLock)
@@ -51,9 +41,9 @@ namespace Avalonia.Win32.DirectX
             }
         }
 
-        private unsafe void RunLoop()
+        private void RunLoop()
         {
-            _stopwatch = System.Diagnostics.Stopwatch.StartNew();
+            _stopwatch = Stopwatch.StartNew();
             try
             {
                 GetBestOutputToVWaitOn();
@@ -162,7 +152,7 @@ namespace Avalonia.Win32.DirectX
         }
 
         // Used the windows composition as a blueprint for this startup/creation 
-        static private bool TryCreateAndRegisterCore()
+        private static bool TryCreateAndRegisterCore()
         {
             var tcs = new TaskCompletionSource<bool>();
             var pumpLock = new object();
@@ -170,9 +160,7 @@ namespace Avalonia.Win32.DirectX
             {
                 try
                 {
-                    DxgiConnection connection;
+                    var connection = new DxgiConnection(pumpLock);
-
-                    connection = new DxgiConnection(pumpLock);
 
                     AvaloniaLocator.CurrentMutable.BindToSelf(connection);
                     AvaloniaLocator.CurrentMutable.Bind<IRenderTimer>().ToConstant(connection);
@@ -191,6 +179,4 @@ namespace Avalonia.Win32.DirectX
             return tcs.Task.Result;
         }
     }
-#nullable restore
-#pragma warning restore CA1416 // Validate platform compatibility
 }

src/Windows/Avalonia.Win32/DirectX/DxgiRenderTarget.cs

@@ -1,40 +1,28 @@
 using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Linq;
-using System.Runtime.InteropServices;
-using System.Text;
-using System.Threading.Tasks;
-using Avalonia.OpenGL.Angle;
 using Avalonia.OpenGL.Egl;
 using Avalonia.OpenGL.Surfaces;
 using Avalonia.Win32.OpenGl.Angle;
 using MicroCom.Runtime;
-using static Avalonia.OpenGL.Egl.EglGlPlatformSurfaceBase;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia.Win32.DirectX
 {
-#pragma warning disable CA1416 // Validate platform compatibility, if you enter this not on windows you have messed up badly 
-#nullable enable
     public unsafe class DxgiRenderTarget : EglPlatformSurfaceRenderTargetBase
     {
         // DXGI_FORMAT_B8G8R8A8_UNORM is target texture format as per ANGLE documentation 
 
         public const uint DXGI_USAGE_RENDER_TARGET_OUTPUT = 0x00000020U;
+        private readonly Guid ID3D11Texture2DGuid = Guid.Parse("6F15AAF2-D208-4E89-9AB4-489535D34F9C");
 
-        private EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo _window;
+        private readonly EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo _window;
-        private DxgiConnection _connection;
+        private readonly DxgiConnection _connection;
-        private IDXGIDevice? _dxgiDevice = null;
+        private readonly IDXGIDevice? _dxgiDevice;
-        private IDXGIFactory2? _dxgiFactory = null;
+        private readonly IDXGIFactory2? _dxgiFactory;
-        private IDXGISwapChain1? _swapChain = null;
+        private readonly IDXGISwapChain1? _swapChain;
-        private IUnknown? _renderTexture = null;
+        private readonly uint _flagsUsed;
 
-        private Interop.UnmanagedMethods.RECT _clientRect = default;
+        private IUnknown? _renderTexture;
-
+        private RECT _clientRect;
-        private uint _flagsUsed;
-
-        private Guid ID3D11Texture2DGuid = Guid.Parse("6F15AAF2-D208-4E89-9AB4-489535D34F9C");
 
         public DxgiRenderTarget(EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo window, EglContext context, DxgiConnection connection) : base(context)
         {
@@ -80,11 +68,11 @@ namespace Avalonia.Win32.DirectX
                     null
             );
 
-            Interop.UnmanagedMethods.RECT pClientRect;
+            GetClientRect(_window.Handle, out var pClientRect);
-            GetClientRect(_window.Handle, out pClientRect);
             _clientRect = pClientRect;
         }
 
+        /// <inheritdoc />
         public override IGlPlatformSurfaceRenderingSession BeginDrawCore()
         {
             if (_swapChain is null)
@@ -98,8 +86,7 @@ namespace Avalonia.Win32.DirectX
             var success = false;
             try
             {
-                Interop.UnmanagedMethods.RECT pClientRect;
+                GetClientRect(_window.Handle, out var pClientRect);
-                GetClientRect(_window.Handle, out pClientRect);
                 if (!RectsEqual(pClientRect, _clientRect))
                 {
                     // we gotta resize 
@@ -137,7 +124,7 @@ namespace Avalonia.Win32.DirectX
                 var res = base.BeginDraw(surface, _window.Size, _window.Scaling, () =>
                 {
                     _swapChain.Present((ushort)0U, (ushort)0U);
-                    surface?.Dispose();
+                    surface.Dispose();
                     transaction?.Dispose();
                     contextLock?.Dispose();
                 }, true);
@@ -178,6 +165,4 @@ namespace Avalonia.Win32.DirectX
         }
 
     }
-#pragma warning restore CA1416 // Validate platform compatibility
-#nullable restore
 }

src/Windows/Avalonia.Win32/FramebufferManager.cs

@@ -4,8 +4,6 @@ using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Platform;
 using Avalonia.Win32.Interop;
 
-#nullable enable
-
 namespace Avalonia.Win32
 {
     internal class FramebufferManager : IFramebufferPlatformSurface, IDisposable

src/Windows/Avalonia.Win32/Input/Imm32InputMethod.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Text;
 using Avalonia.Input.TextInput;
 using Avalonia.Threading;
@@ -10,21 +11,21 @@ namespace Avalonia.Win32.Input
     /// <summary>
     /// A Windows input method editor based on Windows Input Method Manager (IMM32).
     /// </summary>
-    class Imm32InputMethod : ITextInputMethodImpl
+    internal class Imm32InputMethod : ITextInputMethodImpl
     {
-        public IntPtr HWND { get; private set; }
+        public IntPtr Hwnd { get; private set; }
         private IntPtr _currentHimc;
-        private WindowImpl _parent;
+        private WindowImpl? _parent;
-        private ITextInputMethodClient _client;
 
-        private Imm32CaretManager _caretManager = new();
+        private Imm32CaretManager _caretManager;
 
         private ushort _langId;
-        private const int _caretMargin = 1;
+        private const int CaretMargin = 1;
 
-        public ITextInputMethodClient Client => _client;
+        public ITextInputMethodClient? Client { get; private set; }
 
-        public bool IsActive => _client != null;
+        [MemberNotNullWhen(true, nameof(Client))]
+        public bool IsActive => Client != null;
 
         public bool IsComposing { get; set; }
 
@@ -32,12 +33,12 @@ namespace Avalonia.Win32.Input
 
         public void CreateCaret()
         {
-            _caretManager.TryCreate(HWND);
+            _caretManager.TryCreate(Hwnd);
         }
 
         public void EnableImm()
         {
-            var himc = ImmGetContext(HWND);
+            var himc = ImmGetContext(Hwnd);
 
             if(himc == IntPtr.Zero)
             {
@@ -51,13 +52,13 @@ namespace Avalonia.Win32.Input
                     DisableImm();
                 }
 
-                ImmAssociateContext(HWND, himc);
+                ImmAssociateContext(Hwnd, himc);
 
-                ImmReleaseContext(HWND, himc);
+                ImmReleaseContext(Hwnd, himc);
 
                 _currentHimc = himc;
 
-                _caretManager.TryCreate(HWND);
+                _caretManager.TryCreate(Hwnd);
             }
         }
 
@@ -67,7 +68,7 @@ namespace Avalonia.Win32.Input
 
             Reset();
 
-            ImmAssociateContext(HWND, IntPtr.Zero);
+            ImmAssociateContext(Hwnd, IntPtr.Zero);
 
             _caretManager.TryDestroy();
 
@@ -76,7 +77,7 @@ namespace Avalonia.Win32.Input
 
         public void SetLanguageAndWindow(WindowImpl parent, IntPtr hwnd, IntPtr HKL)
         {
-            HWND = hwnd;
+            Hwnd = hwnd;
             _parent = parent;
             _langId = PRIMARYLANGID(LGID(HKL));
 
@@ -98,9 +99,9 @@ namespace Avalonia.Win32.Input
         {
             DisableImm();
 
-            HWND = IntPtr.Zero;
+            Hwnd = IntPtr.Zero;
             _parent = null;
-            _client = null;
+            Client = null;
             _langId = 0;
 
             IsComposing = false;
@@ -108,13 +109,13 @@ namespace Avalonia.Win32.Input
 
         //Dependant on CurrentThread. When Avalonia will support Multiple Dispatchers -
         //every Dispatcher should have their own InputMethod.
-        public static Imm32InputMethod Current { get; } = new Imm32InputMethod();    
+        public static Imm32InputMethod Current { get; } = new();
 
         public void Reset()
         {
             Dispatcher.UIThread.Post(() =>
             {
-                var himc = ImmGetContext(HWND);
+                var himc = ImmGetContext(Hwnd);
 
                 if (IsComposing)
                 {
@@ -123,13 +124,13 @@ namespace Avalonia.Win32.Input
                     IsComposing = false;
                 }
 
-                ImmReleaseContext(HWND, himc);
+                ImmReleaseContext(Hwnd, himc);
             });
         }
 
-        public void SetClient(ITextInputMethodClient client)
+        public void SetClient(ITextInputMethodClient? client)
         {
-            _client = client;
+            Client = client;
 
             Dispatcher.UIThread.Post(() =>
             {
@@ -152,7 +153,7 @@ namespace Avalonia.Win32.Input
 
         public void SetCursorRect(Rect rect)
         {
-            var focused = GetActiveWindow() == HWND;
+            var focused = GetActiveWindow() == Hwnd;
 
             if (!focused)
             {
@@ -161,7 +162,7 @@ namespace Avalonia.Win32.Input
 
             Dispatcher.UIThread.Post(() =>
             {
-                var himc = ImmGetContext(HWND);
+                var himc = ImmGetContext(Hwnd);
 
                 if (himc == IntPtr.Zero)
                 {
@@ -170,7 +171,7 @@ namespace Avalonia.Win32.Input
 
                 MoveImeWindow(rect, himc);
 
-                ImmReleaseContext(HWND, himc);
+                ImmReleaseContext(Hwnd, himc);
             });
         }
         
@@ -219,7 +220,7 @@ namespace Avalonia.Win32.Input
                 // the caret to move the position of their candidate windows.
                 // On the other hand, Korean IMEs require the lower-left corner of the
                 // caret to move their candidate windows.
-                y2 += _caretMargin;
+                y2 += CaretMargin;
             }
 
             // Need to return here since some Chinese IMEs would stuck if set
@@ -238,7 +239,7 @@ namespace Avalonia.Win32.Input
                 dwIndex = 0,
                 dwStyle = CFS_EXCLUDE,
                 ptCurrentPos = new POINT {X = x1, Y = y1},
-                rcArea = new RECT {left = x1, top = y1, right = x2, bottom = y2 + _caretMargin}
+                rcArea = new RECT {left = x1, top = y1, right = x2, bottom = y2 + CaretMargin}
             };
 
             ImmSetCandidateWindow(himc, ref excludeRectangle);
@@ -275,34 +276,21 @@ namespace Avalonia.Win32.Input
                 return;
             }
 
-            if(!IsActive || !_client.SupportsPreedit)
+            if(!IsActive || !Client.SupportsPreedit)
             {
                 return;
             }
 
             var composition = GetCompositionString();
 
-            _client.SetPreeditText(composition);
+            Client.SetPreeditText(composition);
         }
         
-        private string GetCompositionString()
+        private string? GetCompositionString()
         {
-            var himc = ImmGetContext(HWND);
+            var himc = ImmGetContext(Hwnd);
 
-            var length = ImmGetCompositionString(himc, GCS.GCS_COMPSTR, IntPtr.Zero, 0);
+            return ImmGetCompositionString(himc, GCS.GCS_COMPSTR);
-
-            var buffer = new byte[length];
-
-            unsafe
-            {
-                fixed (byte* bufferPtr = buffer)
-                {
-                    var error = ImmGetCompositionString(himc, GCS.GCS_COMPSTR, (IntPtr)bufferPtr, (uint)length);
-
-                    return Encoding.Unicode.GetString(buffer, 0, buffer.Length);
-                }
-            }
-          
         }
 
         ~Imm32InputMethod()

src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs

@@ -5,9 +5,10 @@ using Avalonia.Win32.Interop;
 
 namespace Avalonia.Win32.Input
 {
-    class WindowsMouseDevice : MouseDevice
+    internal class WindowsMouseDevice : MouseDevice
     {
         private readonly IPointer _pointer;
+
         public WindowsMouseDevice() : base(WindowsMousePointer.CreatePointer(out var pointer))
         {
             _pointer = pointer;
@@ -15,14 +16,14 @@ namespace Avalonia.Win32.Input
 
         // Normally user should use IPointer.Capture instead of MouseDevice.Capture,
         // But on Windows we need to handle WM_MOUSE capture manually without having access to the Pointer. 
-        internal void Capture(IInputElement control)
+        internal void Capture(IInputElement? control)
         {
             _pointer.Capture(control);
         }
         
         internal class WindowsMousePointer : Pointer
         {
-            private WindowsMousePointer() : base(Pointer.GetNextFreeId(),PointerType.Mouse, true)
+            private WindowsMousePointer() : base(GetNextFreeId(),PointerType.Mouse, true)
             {
             }
             
@@ -31,7 +32,7 @@ namespace Avalonia.Win32.Input
                 return pointer = new WindowsMousePointer();
             }
 
-            protected override void PlatformCapture(IInputElement element)
+            protected override void PlatformCapture(IInputElement? element)
             {
                 var hwnd = (TopLevel.GetTopLevel(element as Visual)?.PlatformImpl as WindowImpl)
                     ?.Handle.Handle;

src/Windows/Avalonia.Win32/Interop/Automation/IGridProvider.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Runtime.InteropServices;
 
 namespace Avalonia.Win32.Interop.Automation
@@ -8,7 +7,7 @@ namespace Avalonia.Win32.Interop.Automation
     [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     public interface IGridProvider
     {
-        IRawElementProviderSimple GetItem(int row, int column); 
+        IRawElementProviderSimple? GetItem(int row, int column);
         int RowCount { get; }
         int ColumnCount { get; }
     }

src/Windows/Avalonia.Win32/Interop/Automation/IRawElementProviderFragment.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Runtime.InteropServices;
 
-#nullable enable
-
 namespace Avalonia.Win32.Interop.Automation
 {
     [ComVisible(true)]

src/Windows/Avalonia.Win32/Interop/Automation/IRawElementProviderFragmentRoot.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Runtime.InteropServices;
 
 namespace Avalonia.Win32.Interop.Automation
@@ -8,7 +7,7 @@ namespace Avalonia.Win32.Interop.Automation
     [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
     public interface IRawElementProviderFragmentRoot : IRawElementProviderFragment
     {
-        IRawElementProviderFragment ElementProviderFromPoint(double x, double y);
+        IRawElementProviderFragment? ElementProviderFromPoint(double x, double y);
-        IRawElementProviderFragment GetFocus();
+        IRawElementProviderFragment? GetFocus();
     }
 }

src/Windows/Avalonia.Win32/Interop/Automation/IRawElementProviderSimple.cs

@@ -1,8 +1,6 @@
 using System;
 using System.Runtime.InteropServices;
 
-#nullable enable
-
 namespace Avalonia.Win32.Interop.Automation
 {
     [Flags]

src/Windows/Avalonia.Win32/Interop/Automation/IRawElementProviderSimple2.cs

@@ -1,7 +1,4 @@
-using System;
+using System.Runtime.InteropServices;
-using System.Runtime.InteropServices;
-
-#nullable enable
 
 namespace Avalonia.Win32.Interop.Automation
 {

src/Windows/Avalonia.Win32/Interop/Automation/ISelectionItemProvider.cs

@@ -1,5 +1,3 @@
-#nullable enable
-using System;
 using System.Runtime.InteropServices;
 
 namespace Avalonia.Win32.Interop.Automation

src/Windows/Avalonia.Win32/Interop/Automation/IValueProvider.cs

@@ -1,8 +1,5 @@
-using System;
 using System.Runtime.InteropServices;
 
-#nullable enable
-
 namespace Avalonia.Win32.Interop.Automation
 {
     [ComVisible(true)]

src/Windows/Avalonia.Win32/Interop/Automation/UiaCoreProviderApi.cs

@@ -71,21 +71,21 @@ namespace Avalonia.Win32.Interop.Automation
         public static extern bool UiaClientsAreListening();
         
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
-        public static extern IntPtr UiaReturnRawElementProvider(IntPtr hwnd, IntPtr wParam, IntPtr lParam, IRawElementProviderSimple el);
+        public static extern IntPtr UiaReturnRawElementProvider(IntPtr hwnd, IntPtr wParam, IntPtr lParam, IRawElementProviderSimple? el);
 
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
         public static extern int UiaHostProviderFromHwnd(IntPtr hwnd, [MarshalAs(UnmanagedType.Interface)] out IRawElementProviderSimple provider);
 
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
-        public static extern int UiaRaiseAutomationEvent(IRawElementProviderSimple provider, int id);
+        public static extern int UiaRaiseAutomationEvent(IRawElementProviderSimple? provider, int id);
 
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
-        public static extern int UiaRaiseAutomationPropertyChangedEvent(IRawElementProviderSimple provider, int id, object oldValue, object newValue);
+        public static extern int UiaRaiseAutomationPropertyChangedEvent(IRawElementProviderSimple? provider, int id, object? oldValue, object? newValue);
 
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
-        public static extern int UiaRaiseStructureChangedEvent(IRawElementProviderSimple provider, StructureChangeType structureChangeType, int[] runtimeId, int runtimeIdLen);
+        public static extern int UiaRaiseStructureChangedEvent(IRawElementProviderSimple? provider, StructureChangeType structureChangeType, int[]? runtimeId, int runtimeIdLen);
 
         [DllImport("UIAutomationCore.dll", CharSet = CharSet.Unicode)]
-        public static extern int UiaDisconnectProvider(IRawElementProviderSimple provider);
+        public static extern int UiaDisconnectProvider(IRawElementProviderSimple? provider);
     }
 }

src/Windows/Avalonia.Win32/Interop/Automation/UiaCoreTypesApi.cs

@@ -63,8 +63,8 @@ namespace Avalonia.Win32.Interop.Automation
             }
 #endif
 
-            var comConfig = AppContext.GetData("System.Runtime.InteropServices.BuiltInComInterop.IsSupported");
+            var comConfig = AppContext.GetData("System.Runtime.InteropServices.BuiltInComInterop.IsSupported") as string;
-            return comConfig == null || bool.Parse(comConfig.ToString());
+            return comConfig == null || bool.Parse(comConfig);
         }
 
         [DllImport("UIAutomationCore.dll", EntryPoint = "UiaLookupId", CharSet = CharSet.Unicode)]

src/Windows/Avalonia.Win32/Interop/TaskBarList.cs

@@ -7,8 +7,8 @@ namespace Avalonia.Win32.Interop
     internal class TaskBarList
     {
         private static IntPtr s_taskBarList;
-        private static HrInit s_hrInitDelegate;
+        private static HrInit? s_hrInitDelegate;
-        private static MarkFullscreenWindow s_markFullscreenWindowDelegate;
+        private static MarkFullscreenWindow? s_markFullscreenWindowDelegate;
 
         /// <summary>
         /// Ported from https://github.com/chromium/chromium/blob/master/ui/views/win/fullscreen_handler.cc
@@ -28,10 +28,7 @@ namespace Avalonia.Win32.Interop
                 {
                     var ptr = (ITaskBarList2VTable**)s_taskBarList.ToPointer();
 
-                    if (s_hrInitDelegate is null)
+                    s_hrInitDelegate ??= Marshal.GetDelegateForFunctionPointer<HrInit>((*ptr)->HrInit);
-                    {
-                        s_hrInitDelegate = Marshal.GetDelegateForFunctionPointer<HrInit>((*ptr)->HrInit);
-                    }
 
                     if (s_hrInitDelegate(s_taskBarList) != HRESULT.S_OK)
                     {
@@ -44,10 +41,8 @@ namespace Avalonia.Win32.Interop
             {
                 var ptr = (ITaskBarList2VTable**)s_taskBarList.ToPointer();
 
-                if (s_markFullscreenWindowDelegate is null)
+                s_markFullscreenWindowDelegate ??=
-                {
+                    Marshal.GetDelegateForFunctionPointer<MarkFullscreenWindow>((*ptr)->MarkFullscreenWindow);
-                    s_markFullscreenWindowDelegate = Marshal.GetDelegateForFunctionPointer<MarkFullscreenWindow>((*ptr)->MarkFullscreenWindow);
-                }
 
                 s_markFullscreenWindowDelegate(s_taskBarList, hwnd, fullscreen);
             }

src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs

@@ -1,14 +1,12 @@
+#nullable enable
+
 using System;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
-using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.ComTypes;
 using System.Text;
-
-using Avalonia.MicroCom;
 using MicroCom.Runtime;
-using Avalonia.Win32.Win32Com;
 
 // ReSharper disable InconsistentNaming
 #pragma warning disable 169, 649
@@ -1092,7 +1090,7 @@ namespace Avalonia.Win32.Interop
         public const int SizeOf_BITMAPINFOHEADER = 40;
 
         [DllImport("user32.dll", ExactSpelling = true, CharSet = CharSet.Auto, SetLastError = true)]
-        unsafe internal static extern int GetMouseMovePointsEx(
+        internal static extern int GetMouseMovePointsEx(
             uint cbSize, MOUSEMOVEPOINT* pointsIn,
             MOUSEMOVEPOINT* pointsBufferOut, int nBufPoints, uint resolution);
 
@@ -1167,7 +1165,7 @@ namespace Avalonia.Win32.Interop
         public static extern IntPtr CreateWindowEx(
            int dwExStyle,
            uint lpClassName,
-           string lpWindowName,
+           string? lpWindowName,
            uint dwStyle,
            int x,
            int y,
@@ -1218,7 +1216,7 @@ namespace Avalonia.Win32.Interop
         public static extern int GetMessageTime();
 
         [DllImport("kernel32.dll")]
-        public static extern IntPtr GetModuleHandle(string lpModuleName);
+        public static extern IntPtr GetModuleHandle(string? lpModuleName);
 
         [DllImport("user32.dll")]
         public static extern int GetSystemMetrics(SystemMetric smIndex);
@@ -1255,7 +1253,7 @@ namespace Avalonia.Win32.Interop
             }
             else
             {
-                return (uint)SetWindowLong64b(hWnd, nIndex, new IntPtr((uint)value)).ToInt32();
+                return (uint)SetWindowLong64b(hWnd, nIndex, new IntPtr(value)).ToInt32();
             }
         }
 
@@ -1421,7 +1419,7 @@ namespace Avalonia.Win32.Interop
         public static extern bool UnregisterClass(string lpClassName, IntPtr hInstance);
 
         [DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Unicode, EntryPoint = "SetWindowTextW")]
-        public static extern bool SetWindowText(IntPtr hwnd, string lpString);
+        public static extern bool SetWindowText(IntPtr hwnd, string? lpString);
 
         public enum ClassLongIndex : int
         {
@@ -1482,7 +1480,7 @@ namespace Avalonia.Win32.Interop
         internal static extern int CoCreateInstance(ref Guid clsid,
             IntPtr ignore1, int ignore2, ref Guid iid, [Out] out IntPtr pUnkOuter);
 
-        internal unsafe static T CreateInstance<T>(ref Guid clsid, ref Guid iid) where T : IUnknown
+        internal static T CreateInstance<T>(ref Guid clsid, ref Guid iid) where T : IUnknown
         {
             var hresult = CoCreateInstance(ref clsid, IntPtr.Zero, 1, ref iid, out IntPtr pUnk);
             if (hresult != 0)
@@ -1490,7 +1488,7 @@ namespace Avalonia.Win32.Interop
                 throw new COMException("CreateInstance", hresult);
             }
             using var unk = MicroComRuntime.CreateProxyFor<IUnknown>(pUnk, true);
-            return MicroComRuntime.QueryInterface<T>(unk);
+            return unk.QueryInterface<T>();
         }
 
         [DllImport("shell32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
@@ -1581,7 +1579,7 @@ namespace Avalonia.Win32.Interop
         public static extern bool GetMonitorInfo([In] IntPtr hMonitor, ref MONITORINFO lpmi);
 
         [DllImport("user32")]
-        public static extern unsafe bool GetTouchInputInfo(
+        public static extern bool GetTouchInputInfo(
             IntPtr hTouchInput,
             uint cInputs,
             TOUCHINPUT* pInputs,
@@ -1680,7 +1678,7 @@ namespace Avalonia.Win32.Interop
         public static extern IntPtr GlobalSize(IntPtr hGlobal);
 
         [DllImport("shell32.dll", BestFitMapping = false, CharSet = CharSet.Auto)]
-        public static extern int DragQueryFile(IntPtr hDrop, int iFile, StringBuilder lpszFile, int cch);
+        public static extern int DragQueryFile(IntPtr hDrop, int iFile, StringBuilder? lpszFile, int cch);
 
         [DllImport("ole32.dll", CharSet = CharSet.Auto, ExactSpelling = true, PreserveSig = false)]
         internal static extern void DoDragDrop(IntPtr dataObject, IntPtr dropSource, int allowedEffects, [Out] out int finalEffect);
@@ -1734,7 +1732,7 @@ namespace Avalonia.Win32.Interop
 
             public DWM_BLURBEHIND(bool enabled)
             {
-                fEnable = enabled ? true : false;
+                fEnable = enabled;
                 hRgnBlur = IntPtr.Zero;
                 fTransitionOnMaximized = false;
                 dwFlags = DWM_BB.Enable;
@@ -1855,20 +1853,22 @@ namespace Avalonia.Win32.Interop
         [DllImport("imm32.dll", SetLastError = false, CharSet = CharSet.Unicode)]
         public static extern int ImmGetCompositionString(IntPtr hIMC, GCS dwIndex, [Out, Optional] IntPtr lpBuf, uint dwBufLen);
 
-        public static string ImmGetCompositionString(IntPtr hIMC, GCS dwIndex)
+        public static string? ImmGetCompositionString(IntPtr hIMC, GCS dwIndex)
         {
             int bufferLength = ImmGetCompositionString(hIMC, dwIndex, IntPtr.Zero, 0);
 
             if (bufferLength > 0)
             {
-                var buffer = new byte[bufferLength];
+                var buffer = bufferLength <= 64 ? stackalloc byte[bufferLength] : new byte[bufferLength];
 
-                fixed(byte* bufferPtr = buffer)
+                fixed (byte* bufferPtr = buffer)
                 {
-                    var error = ImmGetCompositionString(hIMC, dwIndex, (IntPtr)bufferPtr, (uint)bufferLength);
+                    var result = ImmGetCompositionString(hIMC, dwIndex, (IntPtr)bufferPtr, (uint)bufferLength);
-
+                    if (result >= 0)
-                    return Marshal.PtrToStringUni((IntPtr)bufferPtr);
+                    {
-                }           
+                        return Marshal.PtrToStringUni((IntPtr)bufferPtr);
+                    }
+                }
             }
 
             return null;
@@ -2380,7 +2380,7 @@ namespace Avalonia.Win32.Interop
         }
     }
 
-    [StructLayoutAttribute(LayoutKind.Sequential)]
+    [StructLayout(LayoutKind.Sequential)]
     internal struct _DROPFILES
     {
         public Int32 pFiles;
@@ -2390,7 +2390,7 @@ namespace Avalonia.Win32.Interop
         public bool fWide;
     }
 
-    [StructLayoutAttribute(LayoutKind.Sequential)]
+    [StructLayout(LayoutKind.Sequential)]
     internal struct STGMEDIUM
     {
         public TYMED tymed;
@@ -2398,7 +2398,7 @@ namespace Avalonia.Win32.Interop
         public IntPtr pUnkForRelease;
     }
 
-    [StructLayoutAttribute(LayoutKind.Sequential)]
+    [StructLayout(LayoutKind.Sequential)]
     internal struct FORMATETC
     {
         public ushort cfFormat;
@@ -2507,14 +2507,14 @@ namespace Avalonia.Win32.Interop
         public int uCallbackMessage;
         public IntPtr hIcon;
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
-        public string szTip;
+        public string? szTip;
         public int dwState = 0;
         public int dwStateMask = 0;
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
-        public string szInfo;
+        public string? szInfo;
         public int uTimeoutOrVersion;
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)]
-        public string szInfoTitle;
+        public string? szInfoTitle;
         public NIIF dwInfoFlags;
     }
 }

src/Windows/Avalonia.Win32/NonPumpingSyncContext.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Runtime.ConstrainedExecution;
 using System.Threading;
-using Avalonia.Threading;
 using Avalonia.Utilities;
 using Avalonia.Win32.Interop;
 
@@ -18,8 +17,8 @@ namespace Avalonia.Win32
             SetSynchronizationContext(this);
         }
 
-        public override void Post(SendOrPostCallback d, object state) => _inner.Post(d, state);
+        public override void Post(SendOrPostCallback d, object? state) => _inner.Post(d, state);
-        public override void Send(SendOrPostCallback d, object state) => _inner.Send(d, state);
+        public override void Send(SendOrPostCallback d, object? state) => _inner.Send(d, state);
 
 #if !NET6_0_OR_GREATER
         [PrePrepareMethod]
@@ -32,23 +31,15 @@ namespace Avalonia.Win32
 
         public void Dispose() => SetSynchronizationContext(_inner);
 
-        public static IDisposable Use()
+        public static IDisposable? Use()
         {
             var current = Current;
-            if (current == null)
+            return current is null or NonPumpingSyncContext ? null : new NonPumpingSyncContext(current);
-            {
-                if (Thread.CurrentThread.GetApartmentState() != ApartmentState.STA)
-                    return null;
-            }
-            if (current is NonPumpingSyncContext)
-                return null;
-            
-            return new NonPumpingSyncContext(current);
         }
 
         internal class HelperImpl : NonPumpingLockHelper.IHelperImpl
         {
-            IDisposable NonPumpingLockHelper.IHelperImpl.Use() => NonPumpingSyncContext.Use();
+            IDisposable? NonPumpingLockHelper.IHelperImpl.Use() => NonPumpingSyncContext.Use();
         }
     }
 }

src/Windows/Avalonia.Win32/OffscreenParentWindow.cs

@@ -1,17 +1,18 @@
 using System;
 using System.ComponentModel;
 using System.Runtime.InteropServices;
-using Avalonia.Platform;
 using Avalonia.Win32.Interop;
 namespace Avalonia.Win32
 {
-    class OffscreenParentWindow
+    internal class OffscreenParentWindow
     {
         public static IntPtr Handle { get; } = CreateParentWindow();
-        private static UnmanagedMethods.WndProc s_wndProcDelegate;
+
+        private static UnmanagedMethods.WndProc? s_wndProcDelegate;
+
         private static IntPtr CreateParentWindow()
         {
-            s_wndProcDelegate = new UnmanagedMethods.WndProc(ParentWndProc);
+            s_wndProcDelegate = ParentWndProc;
 
             var wndClassEx = new UnmanagedMethods.WNDCLASSEX
             {

src/Windows/Avalonia.Win32/OleContext.cs

@@ -11,18 +11,16 @@ namespace Avalonia.Win32
 {
     internal class OleContext
     {
-        private static OleContext s_current;
+        private static OleContext? s_current;
 
-        internal static OleContext Current
+        internal static OleContext? Current
         {
             get
             {
                 if (!IsValidOleThread())
                     return null;
 
-                if (s_current == null)
+                return s_current ??= new OleContext();
-                    s_current = new OleContext();
-                return s_current;
             }
         }
 
@@ -41,7 +39,7 @@ namespace Avalonia.Win32
                    Thread.CurrentThread.GetApartmentState() == ApartmentState.STA;
         }
 
-        internal bool RegisterDragDrop(IPlatformHandle hwnd, IDropTarget target)
+        internal bool RegisterDragDrop(IPlatformHandle? hwnd, IDropTarget? target)
         {
             if (hwnd?.HandleDescriptor != "HWND" || target == null)
             {
@@ -52,7 +50,7 @@ namespace Avalonia.Win32
             return UnmanagedMethods.RegisterDragDrop(hwnd.Handle, trgPtr) == UnmanagedMethods.HRESULT.S_OK;
         }
 
-        internal bool UnregisterDragDrop(IPlatformHandle hwnd)
+        internal bool UnregisterDragDrop(IPlatformHandle? hwnd)
         {
             if (hwnd?.HandleDescriptor != "HWND")
             {

src/Windows/Avalonia.Win32/OleDataObject.cs

@@ -8,7 +8,6 @@ using System.Runtime.InteropServices;
 using System.Runtime.InteropServices.ComTypes;
 using System.Runtime.Serialization.Formatters.Binary;
 using Avalonia.Input;
-using Avalonia.MicroCom;
 using Avalonia.Utilities;
 using Avalonia.Win32.Interop;
 using MicroCom.Runtime;
@@ -35,23 +34,23 @@ namespace Avalonia.Win32
             return GetDataFormatsCore().Distinct();
         }
 
-        public string GetText()
+        public string? GetText()
         {
-            return (string)GetDataFromOleHGLOBAL(DataFormats.Text, DVASPECT.DVASPECT_CONTENT);
+            return (string?)GetDataFromOleHGLOBAL(DataFormats.Text, DVASPECT.DVASPECT_CONTENT);
         }
 
-        public IEnumerable<string> GetFileNames()
+        public IEnumerable<string>? GetFileNames()
         {
-            return (IEnumerable<string>)GetDataFromOleHGLOBAL(DataFormats.FileNames, DVASPECT.DVASPECT_CONTENT);
+            return (IEnumerable<string>?)GetDataFromOleHGLOBAL(DataFormats.FileNames, DVASPECT.DVASPECT_CONTENT);
         }
 
-        public object Get(string dataFormat)
+        public object? Get(string dataFormat)
         {
             return GetDataFromOleHGLOBAL(dataFormat, DVASPECT.DVASPECT_CONTENT);
         }
 
         [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "We still use BinaryFormatter for WinForms dragndrop compatability")]
-        private unsafe object GetDataFromOleHGLOBAL(string format, DVASPECT aspect)
+        private unsafe object? GetDataFromOleHGLOBAL(string format, DVASPECT aspect)
         {
             var formatEtc = new Interop.FORMATETC();
             formatEtc.cfFormat = ClipboardFormats.GetFormat(format);
@@ -100,7 +99,7 @@ namespace Avalonia.Win32
 
         private static IEnumerable<string> ReadFileNamesFromHGlobal(IntPtr hGlobal)
         {
-            List<string> files = new List<string>();
+            var files = new List<string>();
             int fileCount = UnmanagedMethods.DragQueryFile(hGlobal, -1, null, 0);
             if (fileCount > 0)
             {
@@ -118,7 +117,7 @@ namespace Avalonia.Win32
             return files;
         }
 
-        private static string ReadStringFromHGlobal(IntPtr hGlobal)
+        private static string? ReadStringFromHGlobal(IntPtr hGlobal)
         {
             IntPtr ptr = UnmanagedMethods.GlobalLock(hGlobal);
             try

src/Windows/Avalonia.Win32/OleDropTarget.cs

@@ -1,5 +1,5 @@
 using System;
-
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
 using Avalonia.MicroCom;
@@ -13,16 +13,16 @@ namespace Avalonia.Win32
     internal class OleDropTarget : CallbackBase, Win32Com.IDropTarget
     {
         private readonly IInputRoot _target;
-        private readonly ITopLevelImpl _tl;
+        private readonly ITopLevelImpl _topLevel;
         private readonly IDragDropDevice _dragDevice;
         
-        private IDataObject _currentDrag = null;
+        private IDataObject? _currentDrag;
 
-        public OleDropTarget(ITopLevelImpl tl, IInputRoot target)
+        public OleDropTarget(ITopLevelImpl topLevel, IInputRoot target, IDragDropDevice dragDevice)
         {
-            _dragDevice = AvaloniaLocator.Current.GetService<IDragDropDevice>();
+            _topLevel = topLevel;
-            _tl = tl;
             _target = target;
+            _dragDevice = dragDevice;
         }
 
         public static DropEffect ConvertDropEffect(DragDropEffects operation)
@@ -71,10 +71,11 @@ namespace Avalonia.Win32
 
         unsafe void Win32Com.IDropTarget.DragEnter(Win32Com.IDataObject pDataObj, int grfKeyState, UnmanagedMethods.POINT pt, DropEffect* pdwEffect)
         {
-            var dispatch = _tl?.Input;
+            var dispatch = _topLevel.Input;
             if (dispatch == null)
             {
                 *pdwEffect= (int)DropEffect.None;
+                return;
             }
 
             SetDataObject(pDataObj);
@@ -94,10 +95,11 @@ namespace Avalonia.Win32
 
         unsafe void Win32Com.IDropTarget.DragOver(int grfKeyState, UnmanagedMethods.POINT pt, DropEffect* pdwEffect)
         {
-            var dispatch = _tl?.Input;
+            var dispatch = _topLevel.Input;
-            if (dispatch == null)
+            if (dispatch == null || _currentDrag is null)
             {
                 *pdwEffect = (int)DropEffect.None;
+                return;
             }
             
             var args = new RawDragEvent(
@@ -115,14 +117,20 @@ namespace Avalonia.Win32
 
         void Win32Com.IDropTarget.DragLeave()
         {
+            var dispatch = _topLevel.Input;
+            if (dispatch == null || _currentDrag is null)
+            {
+                return;
+            }
+
             try
             {
-                _tl?.Input(new RawDragEvent(
+                dispatch(new RawDragEvent(
                     _dragDevice,
                     RawDragEventType.DragLeave,
                     _target,
                     default,
-                    null,
+                    _currentDrag,
                     DragDropEffects.None,
                     RawInputModifiers.None
                 ));
@@ -137,10 +145,11 @@ namespace Avalonia.Win32
         {
             try
             {
-                var dispatch = _tl?.Input;
+                var dispatch = _topLevel.Input;
                 if (dispatch == null)
                 {
                     *pdwEffect = (int)DropEffect.None;
+                    return;
                 }
 
                 SetDataObject(pDataObj);
@@ -163,6 +172,7 @@ namespace Avalonia.Win32
             }
         }
 
+        [MemberNotNull(nameof(_currentDrag))]
         private void SetDataObject(Win32Com.IDataObject pDataObj)
         {
             var newDrag = GetAvaloniaObjectFromCOM(pDataObj);
@@ -178,9 +188,9 @@ namespace Avalonia.Win32
             // OleDataObject keeps COM reference, so it should be disposed.
             if (_currentDrag is OleDataObject oleDragSource)
             {
-                oleDragSource?.Dispose();
+                oleDragSource.Dispose();
-                _currentDrag = null;
             }
+            _currentDrag = null;
         }
 
         private Point GetDragLocation(UnmanagedMethods.POINT dragPoint)
@@ -194,7 +204,7 @@ namespace Avalonia.Win32
             ReleaseDataObject();
         }
 
-        public static unsafe IDataObject GetAvaloniaObjectFromCOM(Win32Com.IDataObject pDataObj)
+        public static IDataObject GetAvaloniaObjectFromCOM(Win32Com.IDataObject pDataObj)
         {
             if (pDataObj is null)
             {
@@ -205,8 +215,7 @@ namespace Avalonia.Win32
                 return disposableDataObject;
             }
 
-            var dataObject = MicroComRuntime.TryUnwrapManagedObject(pDataObj) as DataObject;
+            if (MicroComRuntime.TryUnwrapManagedObject(pDataObj) is DataObject dataObject)
-            if (dataObject is not null)
             {
                 return dataObject;
             }

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleD3DTextureFeature.cs

@@ -14,7 +14,7 @@ internal class AngleD3DTextureFeature  : IGlPlatformSurfaceRenderTargetFactory
             Display: AngleWin32EglDisplay { PlatformApi: AngleOptions.PlatformApi.DirectX11 }
         } && surface is IDirect3D11TexturePlatformSurface;
 
-    class RenderTargetWrapper : EglPlatformSurfaceRenderTargetBase
+    private class RenderTargetWrapper : EglPlatformSurfaceRenderTargetBase
     {
         private readonly AngleWin32EglDisplay _angle;
         private readonly IDirect3D11TextureRenderTarget _target;
@@ -31,8 +31,8 @@ internal class AngleD3DTextureFeature  : IGlPlatformSurfaceRenderTargetFactory
         {
             var success = false;
             var contextLock = Context.EnsureCurrent();
-            IDirect3D11TextureRenderTargetRenderSession session = null;
+            IDirect3D11TextureRenderTargetRenderSession? session = null;
-            EglSurface surface = null;
+            EglSurface? surface = null;
             try
             {
                 try

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleEglInterface.cs

@@ -22,7 +22,7 @@ namespace Avalonia.OpenGL.Angle
         }
         
         [GetProcAddress("eglCreateDeviceANGLE", true)]
-        public partial IntPtr CreateDeviceANGLE(int deviceType, IntPtr nativeDevice, int[] attribs);
+        public partial IntPtr CreateDeviceANGLE(int deviceType, IntPtr nativeDevice, int[]? attribs);
 
         [GetProcAddress("eglReleaseDeviceANGLE", true)]
         public partial void ReleaseDeviceANGLE(IntPtr device);

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleExternalD3D11Texture2D.cs

@@ -1,8 +1,5 @@
-#nullable enable
 using System;
-using System.Threading;
 using Avalonia.OpenGL;
-using Avalonia.OpenGL.Angle;
 using Avalonia.OpenGL.Egl;
 using Avalonia.Platform;
 using Avalonia.Win32.DirectX;
@@ -15,9 +12,12 @@ namespace Avalonia.Win32.OpenGl.Angle;
 internal class AngleExternalMemoryD3D11Texture2D : IGlExternalImageTexture
 {
     private readonly EglContext _context;
-    private ID3D11Texture2D _texture2D;
+    private ID3D11Texture2D? _texture2D;
-    private EglSurface _eglSurface;
+    private EglSurface? _eglSurface;
-    private IDXGIKeyedMutex _mutex;
+    private IDXGIKeyedMutex? _mutex;
+
+    private IDXGIKeyedMutex Mutex
+        => _mutex ?? throw new ObjectDisposedException(nameof(AngleExternalMemoryD3D11Texture2D));
 
     public unsafe AngleExternalMemoryD3D11Texture2D(EglContext context, ID3D11Texture2D texture2D, PlatformGraphicsExternalImageProperties props)
     {
@@ -40,14 +40,14 @@ internal class AngleExternalMemoryD3D11Texture2D : IGlExternalImageTexture
         int temp = 0;
         gl.GenTextures(1, &temp);
         TextureId = temp;
-        gl.BindTexture(GlConsts.GL_TEXTURE_2D, TextureId);
+        gl.BindTexture(GL_TEXTURE_2D, TextureId);
 
         if (_context.Display.EglInterface.BindTexImage(_context.Display.Handle, _eglSurface.DangerousGetHandle(),
                 EGL_BACK_BUFFER) == 0)
             
             throw OpenGlException.GetFormattedException("eglBindTexImage", _context.Display.EglInterface);
     }
-    
+
     public void Dispose()
     {
         
@@ -56,17 +56,15 @@ internal class AngleExternalMemoryD3D11Texture2D : IGlExternalImageTexture
                 _context.GlInterface.DeleteTexture(TextureId);
         TextureId = 0;
         _eglSurface?.Dispose();
-        _eglSurface = null!;
+        _eglSurface = null;
         _texture2D?.Dispose();
-        _texture2D = null!;
+        _texture2D = null;
         _mutex?.Dispose();
-        _mutex = null!;
+        _mutex = null;
     }
 
-
+    public void AcquireKeyedMutex(uint key) => Mutex.AcquireSync(key, int.MaxValue);
-    public void AcquireKeyedMutex(uint key) => _mutex.AcquireSync(key, int.MaxValue);
+    public void ReleaseKeyedMutex(uint key) => Mutex.ReleaseSync(key);
-
-    public void ReleaseKeyedMutex(uint key) => _mutex.ReleaseSync(key);
 
     public int TextureId { get; private set; }
     public int InternalFormat { get; }
@@ -75,7 +73,7 @@ internal class AngleExternalMemoryD3D11Texture2D : IGlExternalImageTexture
 
 internal class AngleExternalMemoryD3D11ExportedTexture2D : AngleExternalMemoryD3D11Texture2D, IGlExportableExternalImageTexture
 {
-    static IPlatformHandle GetHandle(ID3D11Texture2D texture2D)
+    private static IPlatformHandle GetHandle(ID3D11Texture2D texture2D)
     {
         using var resource = texture2D.QueryInterface<IDXGIResource>();
         return new PlatformHandle(resource.SharedHandle,

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleExternalObjectsFeature.cs

@@ -1,7 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-using Avalonia.Controls.Documents;
 using Avalonia.OpenGL;
 using Avalonia.OpenGL.Egl;
 using Avalonia.Platform;
@@ -93,8 +91,8 @@ internal class AngleExternalObjectsFeature : IGlContextExternalObjectsFeature, I
         return default;
     }
 
-    public byte[] DeviceLuid { get; }
+    public byte[]? DeviceLuid { get; }
-    public byte[] DeviceUuid { get; }
+    public byte[]? DeviceUuid => null;
 
     public void Dispose()
     {

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleWin32EglDisplay.cs

@@ -1,4 +1,3 @@
-#nullable enable annotations
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
@@ -97,7 +96,7 @@ namespace Avalonia.Win32.OpenGl.Angle
                 DirectXUnmanagedMethods.D3D11CreateDevice(chosenAdapter?.GetNativeIntPtr() ?? IntPtr.Zero,
                     D3D_DRIVER_TYPE.D3D_DRIVER_TYPE_UNKNOWN,
                     IntPtr.Zero, 0, featureLevels, (uint)featureLevels.Length,
-                    7, out pD3dDevice, out var featureLevel, null);
+                    7, out pD3dDevice, out _, null);
 
 
             if (pD3dDevice == IntPtr.Zero)

src/Windows/Avalonia.Win32/OpenGl/Angle/AngleWin32PlatformGraphics.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Avalonia.Logging;
 using Avalonia.OpenGL;
@@ -12,11 +13,14 @@ namespace Avalonia.Win32.OpenGl.Angle;
 internal class AngleWin32PlatformGraphics : IPlatformGraphics, IPlatformGraphicsOpenGlContextFactory
 {
     private readonly Win32AngleEglInterface _egl;
-    private AngleWin32EglDisplay _sharedDisplay;
+    private readonly AngleWin32EglDisplay? _sharedDisplay;
-    private EglContext _sharedContext;
+    private EglContext? _sharedContext;
-    public bool UsesSharedContext => PlatformApi == AngleOptions.PlatformApi.DirectX9;
+
+    [MemberNotNullWhen(true, nameof(_sharedDisplay))]
+    public bool UsesSharedContext => _sharedDisplay is not null;
+
+    public AngleOptions.PlatformApi PlatformApi { get; }
 
-    public AngleOptions.PlatformApi PlatformApi { get; } = AngleOptions.PlatformApi.DirectX11;
     public IPlatformGraphicsContext CreateContext()
     {
         if (UsesSharedContext)
@@ -72,7 +76,7 @@ internal class AngleWin32PlatformGraphics : IPlatformGraphics, IPlatformGraphics
     }
 
 
-    public static AngleWin32PlatformGraphics TryCreate(AngleOptions options)
+    public static AngleWin32PlatformGraphics? TryCreate(AngleOptions? options)
     {
         Win32AngleEglInterface egl;
         try
@@ -109,7 +113,7 @@ internal class AngleWin32PlatformGraphics : IPlatformGraphics, IPlatformGraphics
             }
             else
             {
-                AngleWin32EglDisplay sharedDisplay = null;
+                AngleWin32EglDisplay? sharedDisplay = null;
                 try
                 {
                     sharedDisplay = AngleWin32EglDisplay.CreateD3D9Display(egl);

src/Windows/Avalonia.Win32/OpenGl/WglContext.cs

@@ -7,22 +7,22 @@ using Avalonia.Platform;
 using Avalonia.Reactive;
 using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
-using static Avalonia.Win32.OpenGl.WglConsts;
 
 namespace Avalonia.Win32.OpenGl
 {
-    class WglContext : IGlContext
+    internal class WglContext : IGlContext
     {
-        private object _lock = new object();
+        private readonly object _lock = new();
-        private readonly WglContext _sharedWith;
+        private readonly WglContext? _sharedWith;
         private readonly IntPtr _context;
         private readonly IntPtr _hWnd;
         private readonly IntPtr _dc;
         private readonly int _pixelFormat;
         private readonly PixelFormatDescriptor _formatDescriptor;
+
         public IntPtr Handle => _context;
 
-        public WglContext(WglContext sharedWith, GlVersion version, IntPtr context, IntPtr hWnd, IntPtr dc, int pixelFormat,
+        public WglContext(WglContext? sharedWith, GlVersion version, IntPtr context, IntPtr hWnd, IntPtr dc, int pixelFormat,
             PixelFormatDescriptor formatDescriptor)
         {
             Version = version;
@@ -54,7 +54,7 @@ namespace Avalonia.Win32.OpenGl
 
         public GlVersion Version { get; }
         public GlInterface GlInterface { get; }
-        public int SampleCount { get; }
+        public int SampleCount => 0;
         public int StencilSize { get; }
 
         private bool IsCurrent => wglGetCurrentContext() == _context && wglGetCurrentDC() == _dc;
@@ -97,12 +97,12 @@ namespace Avalonia.Win32.OpenGl
         }
 
         public bool CanCreateSharedContext => true;
-        public IGlContext CreateSharedContext(IEnumerable<GlVersion> preferredVersions = null)
+        public IGlContext? CreateSharedContext(IEnumerable<GlVersion>? preferredVersions = null)
         {
             var versions = preferredVersions?.Append(Version).ToArray() ?? new[] { Version };
             return WglDisplay.CreateContext(versions, _sharedWith ?? this);
         }
 
-        public object TryGetFeature(Type featureType) => null;
+        public object? TryGetFeature(Type featureType) => null;
     }
 }

src/Windows/Avalonia.Win32/OpenGl/WglDisplay.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 using Avalonia.OpenGL;
 using Avalonia.Threading;
@@ -19,29 +20,31 @@ namespace Avalonia.Win32.OpenGl
         private static int _defaultPixelFormat;
         public static IntPtr OpenGl32Handle = LoadLibrary("opengl32");
 
-        private delegate bool WglChoosePixelFormatARBDelegate(IntPtr hdc, int[] piAttribIList, float[] pfAttribFList,
+        private delegate bool WglChoosePixelFormatARBDelegate(IntPtr hdc, int[]? piAttribIList, float[]? pfAttribFList,
             int nMaxFormats, int[] piFormats, out int nNumFormats);
 
-        private static WglChoosePixelFormatARBDelegate WglChoosePixelFormatArb;
+        private static WglChoosePixelFormatARBDelegate? s_wglChoosePixelFormatArb;
 
-        private delegate IntPtr WglCreateContextAttribsARBDelegate(IntPtr hDC, IntPtr hShareContext, int[] attribList);
+        private delegate IntPtr WglCreateContextAttribsARBDelegate(IntPtr hDC, IntPtr hShareContext, int[]? attribList);
 
-        private static WglCreateContextAttribsARBDelegate WglCreateContextAttribsArb;
+        private static WglCreateContextAttribsARBDelegate? s_wglCreateContextAttribsArb;
         
         private delegate void GlDebugMessageCallbackDelegate(IntPtr callback, IntPtr userParam);
 
-        private static GlDebugMessageCallbackDelegate GlDebugMessageCallback;
+        private static GlDebugMessageCallbackDelegate? s_glDebugMessageCallback;
 
         private delegate void DebugCallbackDelegate(int source, int type, int id, int severity, int len, IntPtr message,
             IntPtr userParam);
-        
+
-        static bool Initialize()
+        [MemberNotNullWhen(true, nameof(s_wglChoosePixelFormatArb))]
-        {
+        [MemberNotNullWhen(true, nameof(s_wglCreateContextAttribsArb))]
-            if (!_initialized.HasValue)
+        [MemberNotNullWhen(true, nameof(s_glDebugMessageCallback))]
-                _initialized = InitializeCore();
+        private static bool Initialize() => _initialized ??= InitializeCore();
-            return _initialized.Value;
+
-        }
+        [MemberNotNullWhen(true, nameof(s_wglChoosePixelFormatArb))]
-        static bool InitializeCore()
+        [MemberNotNullWhen(true, nameof(s_wglCreateContextAttribsArb))]
+        [MemberNotNullWhen(true, nameof(s_glDebugMessageCallback))]
+        private static bool InitializeCore()
         {
             Dispatcher.UIThread.VerifyAccess();
             _bootstrapWindow = WglGdiResourceManager.CreateOffscreenWindow();
@@ -64,20 +67,20 @@ namespace Avalonia.Win32.OpenGl
                 return false;
 
             wglMakeCurrent(_bootstrapDc, _bootstrapContext);
-            WglCreateContextAttribsArb = Marshal.GetDelegateForFunctionPointer<WglCreateContextAttribsARBDelegate>(
+            s_wglCreateContextAttribsArb = Marshal.GetDelegateForFunctionPointer<WglCreateContextAttribsARBDelegate>(
                 wglGetProcAddress("wglCreateContextAttribsARB"));
 
-            WglChoosePixelFormatArb =
+            s_wglChoosePixelFormatArb =
                 Marshal.GetDelegateForFunctionPointer<WglChoosePixelFormatARBDelegate>(
                     wglGetProcAddress("wglChoosePixelFormatARB"));
 
-            GlDebugMessageCallback =
+            s_glDebugMessageCallback =
                 Marshal.GetDelegateForFunctionPointer<GlDebugMessageCallbackDelegate>(
                     wglGetProcAddress("glDebugMessageCallback"));
             
 
             var formats = new int[1];
-            WglChoosePixelFormatArb(_bootstrapDc, new int[]
+            s_wglChoosePixelFormatArb(_bootstrapDc, new int[]
             {
                 WGL_DRAW_TO_WINDOW_ARB, 1,
                 WGL_ACCELERATION_ARB, WGL_FULL_ACCELERATION_ARB,
@@ -106,12 +109,12 @@ namespace Avalonia.Win32.OpenGl
             Console.Error.WriteLine(err);
         }
         
-        public static WglContext CreateContext(GlVersion[] versions, IGlContext share)
+        public static WglContext? CreateContext(GlVersion[] versions, IGlContext? share)
         {
             if (!Initialize())
                 return null;
 
-            var shareContext = (WglContext)share;
+            var shareContext = share as WglContext;
 
             using (new WglRestoreContext(_bootstrapDc, _bootstrapContext, null))
             {
@@ -125,7 +128,7 @@ namespace Avalonia.Win32.OpenGl
                     IntPtr context;
                     using (shareContext?.Lock())
                     {
-                        context = WglCreateContextAttribsArb(dc, shareContext?.Handle ?? IntPtr.Zero,
+                        context = s_wglCreateContextAttribsArb(dc, shareContext?.Handle ?? IntPtr.Zero,
                             new[]
                             {
                                 // major
@@ -142,7 +145,7 @@ namespace Avalonia.Win32.OpenGl
                     }
 
                     using(new WglRestoreContext(dc, context, null))
-                        GlDebugMessageCallback(Marshal.GetFunctionPointerForDelegate(_debugCallback), IntPtr.Zero);
+                        s_glDebugMessageCallback(Marshal.GetFunctionPointerForDelegate(_debugCallback), IntPtr.Zero);
                     if (context != IntPtr.Zero)
                         return new WglContext(shareContext, version, context, window, dc,
                             _defaultPixelFormat, _defaultPfd);

src/Windows/Avalonia.Win32/OpenGl/WglGdiResourceManager.cs

@@ -17,45 +17,69 @@ namespace Avalonia.Win32.OpenGl;
 
 internal class WglGdiResourceManager
 {
-    class GetDCOp
+    private class GetDCOp
     {
-        public IntPtr Window;
+        public readonly IntPtr Window;
-        public TaskCompletionSource<IntPtr> Result;
+        public readonly TaskCompletionSource<IntPtr> Result;
+
+        public GetDCOp(IntPtr window, TaskCompletionSource<IntPtr> result)
+        {
+            Window = window;
+            Result = result;
+        }
     }
 
-    class ReleaseDCOp
+    private class ReleaseDCOp
     {
-        public IntPtr Window;
+        public readonly IntPtr Window;
-        public IntPtr DC;
+        public readonly IntPtr DC;
-        public TaskCompletionSource<object> Result;
+        public readonly TaskCompletionSource<object?> Result;
+
+        public ReleaseDCOp(IntPtr window, IntPtr dc, TaskCompletionSource<object?> result)
+        {
+            Window = window;
+            DC = dc;
+            Result = result;
+        }
     }
-    
+
-    class CreateWindowOp
+    private class CreateWindowOp
     {
-        public TaskCompletionSource<IntPtr> Result;
+        public readonly TaskCompletionSource<IntPtr> Result;
+
+        public CreateWindowOp(TaskCompletionSource<IntPtr> result)
+        {
+            Result = result;
+        }
     }
 
-    class DestroyWindowOp
+    private class DestroyWindowOp
     {
-        public IntPtr Window;
+        public readonly IntPtr Window;
-        public TaskCompletionSource<object> Result;
+        public readonly TaskCompletionSource<object?> Result;
+
+        public DestroyWindowOp(IntPtr window, TaskCompletionSource<object?> result)
+        {
+            Window = window;
+            Result = result;
+        }
     }
 
-    private static readonly Queue<object> s_Queue = new();
+    private static readonly Queue<object> s_queue = new();
-    private static readonly AutoResetEvent s_Event = new(false);
+    private static readonly AutoResetEvent s_event = new(false);
-    private static readonly ushort s_WindowClass;
+    private static readonly ushort s_windowClass;
     private static readonly UnmanagedMethods.WndProc s_wndProcDelegate = WndProc;
 
-    static void Worker()
+    private static void Worker()
     {
         while (true)
         {
-            s_Event.WaitOne();
+            s_event.WaitOne();
-            lock (s_Queue)
+            lock (s_queue)
             {
-                if(s_Queue.Count == 0)
+                if(s_queue.Count == 0)
                     continue;
-                var job = s_Queue.Dequeue();
+                var job = s_queue.Dequeue();
                 if (job is GetDCOp getDc)
                     getDc.Result.TrySetResult(UnmanagedMethods.GetDC(getDc.Window));
                 else if (job is ReleaseDCOp releaseDc)
@@ -66,7 +90,7 @@ internal class WglGdiResourceManager
                 else if (job is CreateWindowOp createWindow)
                     createWindow.Result.TrySetResult(UnmanagedMethods.CreateWindowEx(
                         0,
-                        s_WindowClass,
+                        s_windowClass,
                         null,
                         (int)UnmanagedMethods.WindowStyles.WS_OVERLAPPEDWINDOW,
                         0,
@@ -97,16 +121,15 @@ internal class WglGdiResourceManager
             style = (int)UnmanagedMethods.ClassStyles.CS_OWNDC
         };
             
-        s_WindowClass = UnmanagedMethods.RegisterClassEx(ref wndClassEx);
+        s_windowClass = UnmanagedMethods.RegisterClassEx(ref wndClassEx);
         var th = new Thread(Worker) { IsBackground = true, Name = "Win32 OpenGL HDC manager" };
         // This makes CLR to automatically pump the event queue from WaitOne
         th.SetApartmentState(ApartmentState.STA);
         th.Start();
     }
-    
+
-        
+
-    
+    private static IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
-    static IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
     {
         return UnmanagedMethods.DefWindowProc(hWnd, msg, wParam, lParam);
     }
@@ -114,53 +137,36 @@ internal class WglGdiResourceManager
     public static IntPtr CreateOffscreenWindow()
     {
         var tcs = new TaskCompletionSource<IntPtr>();
-        lock(s_Queue)
+        lock (s_queue)
-            s_Queue.Enqueue(new CreateWindowOp()
+            s_queue.Enqueue(new CreateWindowOp(tcs));
-            {
+        s_event.Set();
-                Result = tcs
-            });
-        s_Event.Set();
         return tcs.Task.Result;
     }
     
     public static IntPtr GetDC(IntPtr hWnd)
     {
         var tcs = new TaskCompletionSource<IntPtr>();
-        lock(s_Queue)
+        lock (s_queue)
-            s_Queue.Enqueue(new GetDCOp
+            s_queue.Enqueue(new GetDCOp(hWnd, tcs));
-            {
+        s_event.Set();
-                Window = hWnd,
-                Result = tcs
-            });
-        s_Event.Set();
         return tcs.Task.Result;
     }
 
     public static void ReleaseDC(IntPtr hWnd, IntPtr hDC)
     {
-        var tcs = new TaskCompletionSource<object>();
+        var tcs = new TaskCompletionSource<object?>();
-        lock(s_Queue)
+        lock (s_queue)
-            s_Queue.Enqueue(new ReleaseDCOp()
+            s_queue.Enqueue(new ReleaseDCOp(hWnd, hDC, tcs));
-            {
+        s_event.Set();
-                Window = hWnd,
-                DC = hDC,
-                Result = tcs
-            });
-        s_Event.Set();
         tcs.Task.Wait();
     }
     
     public static void DestroyWindow(IntPtr hWnd)
     {
-        var tcs = new TaskCompletionSource<object>();
+        var tcs = new TaskCompletionSource<object?>();
-        lock(s_Queue)
+        lock (s_queue)
-            s_Queue.Enqueue(new DestroyWindowOp()
+            s_queue.Enqueue(new DestroyWindowOp(hWnd, tcs));
-            {
+        s_event.Set();
-                Window = hWnd,
-                Result = tcs
-            });
-        s_Event.Set();
         tcs.Task.Wait();
-        
     }
 }

src/Windows/Avalonia.Win32/OpenGl/WglPlatformOpenGlInterface.cs

@@ -6,27 +6,31 @@ using Avalonia.Platform;
 
 namespace Avalonia.Win32.OpenGl
 {
-    class WglPlatformOpenGlInterface : IPlatformGraphics
+    internal class WglPlatformOpenGlInterface : IPlatformGraphics
     {
         public WglContext PrimaryContext { get; }
         public bool UsesSharedContext => false;
         IPlatformGraphicsContext IPlatformGraphics.CreateContext() => CreateContext();
         public IPlatformGraphicsContext GetSharedContext() => throw new NotSupportedException();
-        
-        public IGlContext CreateContext() => WglDisplay.CreateContext(new[] { PrimaryContext.Version }, null);
 
-        private  WglPlatformOpenGlInterface(WglContext primary)
+        public IGlContext CreateContext()
+            => WglDisplay.CreateContext(new[] { PrimaryContext.Version }, null)
+               ?? throw new OpenGlException("Unable to create additional WGL context");
+
+        private WglPlatformOpenGlInterface(WglContext primary)
         {
             PrimaryContext = primary;
         }
 
-        public static WglPlatformOpenGlInterface TryCreate()
+        public static WglPlatformOpenGlInterface? TryCreate()
         {
             try
             {
                 var opts = AvaloniaLocator.Current.GetService<Win32PlatformOptions>() ?? new Win32PlatformOptions();
-                var primary = WglDisplay.CreateContext(opts.WglProfiles.ToArray(), null);
+                if (WglDisplay.CreateContext(opts.WglProfiles.ToArray(), null) is { } primary)
-                return new WglPlatformOpenGlInterface(primary);
+                {
+                    return new WglPlatformOpenGlInterface(primary);
+                }
             }
             catch (Exception e)
             {

src/Windows/Avalonia.Win32/OpenGl/WglRestoreContext.cs

@@ -8,11 +8,11 @@ namespace Avalonia.Win32.OpenGl
 {
     internal class WglRestoreContext : IDisposable
     {
-        private readonly object _monitor;
+        private readonly object? _monitor;
         private readonly IntPtr _oldDc;
         private readonly IntPtr _oldContext;
 
-        public WglRestoreContext(IntPtr gc, IntPtr context, object monitor, bool takeMonitor = true)
+        public WglRestoreContext(IntPtr gc, IntPtr context, object? monitor, bool takeMonitor = true)
         {
             _monitor = monitor;
             _oldDc = wglGetCurrentDC();

src/Windows/Avalonia.Win32/PopupImpl.cs

@@ -5,9 +5,9 @@ using Avalonia.Win32.Interop;
 
 namespace Avalonia.Win32
 {
-    class PopupImpl : WindowImpl, IPopupImpl
+    internal class PopupImpl : WindowImpl, IPopupImpl
     {
-        private readonly IWindowBaseImpl _parent;
+        private readonly IWindowBaseImpl? _parent;
         private bool _dropShadowHint = true;
         private Size? _maxAutoSize;
 
@@ -92,7 +92,7 @@ namespace Avalonia.Win32
                 IntPtr.Zero);
             s_parentHandle = IntPtr.Zero;
 
-            PopupImpl.EnableBoxShadow(result, _dropShadowHint);
+            EnableBoxShadow(result, _dropShadowHint);
 
             return result;
         }
@@ -113,7 +113,7 @@ namespace Avalonia.Win32
 
         // This is needed because we are calling virtual methods from constructors
         // One fabulous design decision leads to another, I guess
-        static IWindowBaseImpl SaveParentHandle(IWindowBaseImpl parent)
+        private static IWindowBaseImpl SaveParentHandle(IWindowBaseImpl parent)
         {
             s_parentHandle = parent.Handle.Handle;
             return parent;
@@ -126,7 +126,7 @@ namespace Avalonia.Win32
 
         }
 
-        private PopupImpl(IWindowBaseImpl parent, bool dummy) : base()
+        private PopupImpl(IWindowBaseImpl parent, bool dummy)
         {
             _parent = parent;
             PopupPositioner = new ManagedPopupPositioner(new ManagedPopupPositionerPopupImplHelper(parent, MoveResize));
@@ -159,10 +159,7 @@ namespace Avalonia.Win32
         {
             _dropShadowHint = enabled;
 
-            if (Handle != null)
+            EnableBoxShadow(Handle.Handle, enabled);
-            {
-                PopupImpl.EnableBoxShadow(Handle.Handle, enabled);
-            }
         }
 
         public IPopupPositioner PopupPositioner { get; }

src/Windows/Avalonia.Win32/ScreenImpl.cs

@@ -3,7 +3,6 @@ using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Metadata;
 using Avalonia.Platform;
-using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia.Win32
@@ -11,12 +10,15 @@ namespace Avalonia.Win32
     [Unstable]
     public class ScreenImpl : IScreenImpl
     {
+        private Screen[]? _allScreens;
+
+        /// <inheritdoc />
         public int ScreenCount
         {
             get => GetSystemMetrics(SystemMetric.SM_CMONITORS);
         }
 
-        private Screen[] _allScreens;
+        /// <inheritdoc />
         public IReadOnlyList<Screen> AllScreens
         {
             get
@@ -38,7 +40,7 @@ namespace Avalonia.Win32
                                 if (method != IntPtr.Zero)
                                 {
                                     GetDpiForMonitor(monitor, MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI, out var x, out _);
-                                    dpi = (double)x;
+                                    dpi = x;
                                 }
                                 else
                                 {
@@ -74,7 +76,8 @@ namespace Avalonia.Win32
             _allScreens = null;
         }
 
-        public Screen ScreenFromWindow(IWindowBaseImpl window)
+        /// <inheritdoc />
+        public Screen? ScreenFromWindow(IWindowBaseImpl window)
         {
             var handle = window.Handle.Handle;
 
@@ -83,7 +86,8 @@ namespace Avalonia.Win32
             return FindScreenByHandle(monitor);
         }
 
-        public Screen ScreenFromPoint(PixelPoint point)
+        /// <inheritdoc />
+        public Screen? ScreenFromPoint(PixelPoint point)
         {
             var monitor = MonitorFromPoint(new POINT
             {
@@ -94,7 +98,8 @@ namespace Avalonia.Win32
             return FindScreenByHandle(monitor);
         }
 
-        public Screen ScreenFromRect(PixelRect rect)
+        /// <inheritdoc />
+        public Screen? ScreenFromRect(PixelRect rect)
         {
             var monitor = MonitorFromRect(new RECT
             {
@@ -107,7 +112,7 @@ namespace Avalonia.Win32
             return FindScreenByHandle(monitor);
         }
 
-        private Screen FindScreenByHandle(IntPtr handle)
+        private Screen? FindScreenByHandle(IntPtr handle)
         {
             return AllScreens.Cast<WinScreen>().FirstOrDefault(m => m.Handle == handle);
         }

src/Windows/Avalonia.Win32/TrayIconImpl.cs

@@ -11,8 +11,6 @@ using Avalonia.Styling;
 using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
-#nullable enable
-
 namespace Avalonia.Win32
 {
     [Unstable]
@@ -25,9 +23,9 @@ namespace Avalonia.Win32
         private IconImpl? _icon;
         private string? _tooltipText;
         private readonly Win32NativeToManagedMenuExporter _exporter;
-        private static readonly Dictionary<int, TrayIconImpl> s_trayIcons = new Dictionary<int, TrayIconImpl>();
+        private static readonly Dictionary<int, TrayIconImpl> s_trayIcons = new();
         private bool _disposedValue;
-        private static readonly uint WM_TASKBARCREATED = UnmanagedMethods.RegisterWindowMessage("TaskbarCreated");
+        private static readonly uint WM_TASKBARCREATED = RegisterWindowMessage("TaskbarCreated");
 
         public TrayIconImpl()
         {
@@ -62,17 +60,20 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public void SetIcon(IWindowIconImpl? icon)
         {
             _icon = icon as IconImpl;
             UpdateIcon();
         }
 
+        /// <inheritdoc />
         public void SetIsVisible(bool visible)
         {
             UpdateIcon(!visible);
         }
 
+        /// <inheritdoc />
         public void SetToolTipText(string? text)
         {
             _tooltipText = text;
@@ -209,8 +210,11 @@ namespace Avalonia.Win32
 
             private void MoveResize(PixelPoint position, Size size, double scaling)
             {
-                PlatformImpl!.Move(position);
+                if (PlatformImpl is { } platformImpl)
-                PlatformImpl!.Resize(size, PlatformResizeReason.Layout);
+                {
+                    platformImpl.Move(position);
+                    platformImpl.Resize(size, PlatformResizeReason.Layout);
+                }
             }
 
             protected override void ArrangeCore(Rect finalRect)
@@ -221,7 +225,7 @@ namespace Avalonia.Win32
                 {
                     Anchor = PopupAnchor.TopLeft,
                     Gravity = PopupGravity.BottomRight,
-                    AnchorRectangle = new Rect(Position.ToPoint(1) / Screens.Primary.Scaling, new Size(1, 1)),
+                    AnchorRectangle = new Rect(Position.ToPoint(Screens.Primary?.Scaling ?? 1.0), new Size(1, 1)),
                     Size = finalRect.Size,
                     ConstraintAdjustment = PopupPositionerConstraintAdjustment.FlipX | PopupPositionerConstraintAdjustment.FlipY,
                 });
@@ -247,18 +251,22 @@ namespace Avalonia.Win32
                 {
                     get
                     {
-                        var point = _hiddenWindow.Screens.Primary.Bounds.TopLeft;
+                        if (_hiddenWindow.Screens.Primary is { } screen)
-                        var size = _hiddenWindow.Screens.Primary.Bounds.Size;
+                        {
-                        return new Rect(point.X, point.Y, size.Width * _hiddenWindow.Screens.Primary.Scaling, size.Height * _hiddenWindow.Screens.Primary.Scaling);
+                            var point = screen.Bounds.TopLeft;
+                            var size = screen.Bounds.Size;
+                            return new Rect(point.X, point.Y, size.Width * screen.Scaling, size.Height * screen.Scaling);
+                        }
+                        return default;
                     }
                 }
 
                 public void MoveAndResize(Point devicePoint, Size virtualSize)
                 {
-                    _moveResize(new PixelPoint((int)devicePoint.X, (int)devicePoint.Y), virtualSize, _hiddenWindow.Screens.Primary.Scaling);
+                    _moveResize(new PixelPoint((int)devicePoint.X, (int)devicePoint.Y), virtualSize, Scaling);
                 }
 
-                public double Scaling => _hiddenWindow.Screens.Primary.Scaling;
+                public double Scaling => _hiddenWindow.Screens.Primary?.Scaling ?? 1.0;
             }
         }
 

src/Windows/Avalonia.Win32/Win32GlManager.cs

@@ -1,6 +1,4 @@
 using Avalonia.OpenGL;
-using Avalonia.OpenGL.Angle;
-using Avalonia.OpenGL.Egl;
 using Avalonia.Platform;
 using Avalonia.Win32.DirectX;
 using Avalonia.Win32.OpenGl;
@@ -11,16 +9,19 @@ namespace Avalonia.Win32
 {
     static class Win32GlManager
     {
-
+        public static IPlatformGraphics? Initialize()
-        public static IPlatformGraphics Initialize()
         {
             var gl = InitializeCore();
-            AvaloniaLocator.CurrentMutable.Bind<IPlatformGraphics>().ToConstant(gl);
+
-            AvaloniaLocator.CurrentMutable.Bind<IPlatformGraphics>().ToConstant(gl);
+            if (gl is not null)
+            {
+                AvaloniaLocator.CurrentMutable.Bind<IPlatformGraphics>().ToConstant(gl);
+            }
+
             return gl;
         }
         
-        static IPlatformGraphics InitializeCore()
+        private static IPlatformGraphics? InitializeCore()
         {
 
             var opts = AvaloniaLocator.Current.GetService<Win32PlatformOptions>() ?? new Win32PlatformOptions();
@@ -55,7 +56,5 @@ namespace Avalonia.Win32
 
             return null;
         }
-        
-        
     }
 }

src/Windows/Avalonia.Win32/Win32NativeControlHost.cs

@@ -1,13 +1,13 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 using Avalonia.Controls.Platform;
 using Avalonia.Platform;
-using Avalonia.VisualTree;
 using Avalonia.Win32.Interop;
 
 namespace Avalonia.Win32
 {
-    class Win32NativeControlHost : INativeControlHostImpl
+    internal class Win32NativeControlHost : INativeControlHostImpl
     {
         private readonly bool _useLayeredWindow;
         public WindowImpl Window { get; }
@@ -18,7 +18,7 @@ namespace Avalonia.Win32
             Window = window;
         }
 
-        void AssertCompatible(IPlatformHandle handle)
+        private void AssertCompatible(IPlatformHandle handle)
         {
             if (!IsCompatibleWith(handle))
                 throw new ArgumentException($"Don't know what to do with {handle.HandleDescriptor}");
@@ -33,7 +33,7 @@ namespace Avalonia.Win32
         public INativeControlHostControlTopLevelAttachment CreateNewAttachment(Func<IPlatformHandle, IPlatformHandle> create)
         {
             var holder = new DumbWindow(_useLayeredWindow, Window.Handle.Handle);
-            Win32NativeControlAttachment attachment = null;
+            Win32NativeControlAttachment? attachment = null;
             try
             {
                 var child = create(holder);
@@ -46,7 +46,7 @@ namespace Avalonia.Win32
             catch
             {
                 attachment?.Dispose();
-                holder?.Destroy();
+                holder.Destroy();
                 throw;
             }
         }
@@ -60,13 +60,13 @@ namespace Avalonia.Win32
 
         public bool IsCompatibleWith(IPlatformHandle handle) => handle.HandleDescriptor == "HWND";
 
-        class DumbWindow : IDisposable, INativeControlHostDestroyableControlHandle
+        private class DumbWindow : IDisposable, INativeControlHostDestroyableControlHandle
         {
             public IntPtr Handle { get;}
             public string HandleDescriptor => "HWND";
             public void Destroy() => Dispose();
 
-            UnmanagedMethods.WndProc _wndProcDelegate;
+            private readonly UnmanagedMethods.WndProc _wndProcDelegate;
             private readonly string _className;
 
             public DumbWindow(bool layered = false, IntPtr? parent = null)
@@ -103,9 +103,7 @@ namespace Avalonia.Win32
                         UnmanagedMethods.LayeredWindowFlags.LWA_ALPHA);
             }
 
-
+            private static IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
-
-            protected virtual unsafe IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
             {
                 return UnmanagedMethods.DefWindowProc(hWnd, msg, wParam, lParam);
             }
@@ -128,11 +126,11 @@ namespace Avalonia.Win32
             }
         }
 
-        class Win32NativeControlAttachment : INativeControlHostControlTopLevelAttachment
+        private class Win32NativeControlAttachment : INativeControlHostControlTopLevelAttachment
         {
-            private DumbWindow _holder;
+            private DumbWindow? _holder;
-            private IPlatformHandle _child;
+            private IPlatformHandle? _child;
-            private Win32NativeControlHost _attachedTo;
+            private Win32NativeControlHost? _attachedTo;
 
             public Win32NativeControlAttachment(DumbWindow holder, IPlatformHandle child)
             {
@@ -142,7 +140,8 @@ namespace Avalonia.Win32
                 UnmanagedMethods.ShowWindow(child.Handle, UnmanagedMethods.ShowWindowCommand.Show);
             }
 
-            void CheckDisposed()
+            [MemberNotNull(nameof(_holder))]
+            private void CheckDisposed()
             {
                 if (_holder == null)
                     throw new ObjectDisposedException(nameof(Win32NativeControlAttachment));
@@ -158,13 +157,13 @@ namespace Avalonia.Win32
                 _attachedTo = null;
             }
 
-            public INativeControlHostImpl AttachedTo
+            public INativeControlHostImpl? AttachedTo
             {
                 get => _attachedTo;
                 set
                 {
                     CheckDisposed();
-                    _attachedTo = (Win32NativeControlHost) value;
+                    _attachedTo = value as Win32NativeControlHost;
                     if (_attachedTo == null)
                     {
                         UnmanagedMethods.ShowWindow(_holder.Handle, UnmanagedMethods.ShowWindowCommand.Hide);
@@ -179,6 +178,7 @@ namespace Avalonia.Win32
 
             public void HideWithSize(Size size)
             {
+                CheckDisposed();
                 UnmanagedMethods.SetWindowPos(_holder.Handle, IntPtr.Zero,
                     -100, -100, 1, 1,
                     UnmanagedMethods.SetWindowPosFlags.SWP_HIDEWINDOW |
@@ -198,8 +198,12 @@ namespace Avalonia.Win32
                 bounds *= _attachedTo.Window.RenderScaling;
                 var pixelRect = new PixelRect((int)bounds.X, (int)bounds.Y, Math.Max(1, (int)bounds.Width),
                     Math.Max(1, (int)bounds.Height));
-                
+
-                UnmanagedMethods.MoveWindow(_child.Handle, 0, 0, pixelRect.Width, pixelRect.Height, true);
+                if (_child is not null)
+                {
+                    UnmanagedMethods.MoveWindow(_child.Handle, 0, 0, pixelRect.Width, pixelRect.Height, true);
+                }
+
                 UnmanagedMethods.SetWindowPos(_holder.Handle, IntPtr.Zero, pixelRect.X, pixelRect.Y, pixelRect.Width,
                     pixelRect.Height,
                     UnmanagedMethods.SetWindowPosFlags.SWP_SHOWWINDOW

src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs

@@ -1,12 +1,7 @@
-using System.Collections.Generic;
+using Avalonia.Reactive;
-using Avalonia.Reactive;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
-using Avalonia.Media.Imaging;
-using Avalonia.Utilities;
-
-#nullable enable
 
 namespace Avalonia.Win32
 {
@@ -19,7 +14,7 @@ namespace Avalonia.Win32
             _nativeMenu = nativeMenu;
         }
 
-        private AvaloniaList<MenuItem> Populate(NativeMenu nativeMenu)
+        private static AvaloniaList<MenuItem> Populate(NativeMenu nativeMenu)
         {
             var result = new AvaloniaList<MenuItem>();
             

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -17,12 +17,10 @@ using Avalonia.Rendering.Composition;
 using Avalonia.Threading;
 using Avalonia.Utilities;
 using Avalonia.Win32.Input;
-using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia
 {
-#nullable enable
     public static class Win32ApplicationExtensions
     {
         public static AppBuilder UseWin32(this AppBuilder builder)
@@ -106,17 +104,19 @@ namespace Avalonia
         public IPlatformGraphics? CustomPlatformGraphics { get; set; }
     }
 }
-#nullable restore
 
 namespace Avalonia.Win32
 {
     public class Win32Platform : IPlatformThreadingInterface, IWindowingPlatform, IPlatformIconLoader, IPlatformLifetimeEventsImpl
     {
-        private static readonly Win32Platform s_instance = new Win32Platform();
+        private static readonly Win32Platform s_instance = new();
-        private static Thread _uiThread;
+        private static Thread? s_uiThread;
-        private UnmanagedMethods.WndProc _wndProcDelegate;
+        private static Win32PlatformOptions? s_options;
+        private static Compositor? s_compositor;
+
+        private WndProc? _wndProcDelegate;
         private IntPtr _hwnd;
-        private readonly List<Delegate> _delegates = new List<Delegate>();
+        private readonly List<Delegate> _delegates = new();
 
         public Win32Platform()
         {
@@ -135,9 +135,12 @@ namespace Avalonia.Win32
         public static Version WindowsVersion { get; } = RtlGetVersion();
 
         internal static bool UseOverlayPopups => Options.OverlayPopups;
-        public static Win32PlatformOptions Options { get; private set; }
 
-        internal static Compositor Compositor { get; private set; }
+        public static Win32PlatformOptions Options
+            => s_options ?? throw new InvalidOperationException($"{nameof(Win32Platform)} hasn't been initialized");
+
+        internal static Compositor Compositor
+            => s_compositor ?? throw new InvalidOperationException($"{nameof(Win32Platform)} hasn't been initialized");
 
         public static void Initialize()
         {
@@ -146,7 +149,7 @@ namespace Avalonia.Win32
 
         public static void Initialize(Win32PlatformOptions options)
         {
-            Options = options;
+            s_options = options;
             var renderTimer = options.ShouldRenderOnUIThread ? new UiThreadRenderTimer(60) : new DefaultRenderTimer(60);
 
             AvaloniaLocator.CurrentMutable
@@ -171,26 +174,24 @@ namespace Avalonia.Win32
                 .Bind<IMountedVolumeInfoProvider>().ToConstant(new WindowsMountedVolumeInfoProvider())
                 .Bind<IPlatformLifetimeEventsImpl>().ToConstant(s_instance);
             
-            _uiThread = Thread.CurrentThread;
+            s_uiThread = Thread.CurrentThread;
 
-            var platformGraphics = options?.CustomPlatformGraphics
+            var platformGraphics = options.CustomPlatformGraphics
                                    ?? Win32GlManager.Initialize();
             
             if (OleContext.Current != null)
                 AvaloniaLocator.CurrentMutable.Bind<IPlatformDragSource>().ToSingleton<DragSource>();
             
-            Compositor = new Compositor(AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(), platformGraphics);
+            s_compositor = new Compositor(AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(), platformGraphics);
         }
 
         public bool HasMessages()
         {
-            UnmanagedMethods.MSG msg;
+            return PeekMessage(out _, IntPtr.Zero, 0, 0, 0);
-            return PeekMessage(out msg, IntPtr.Zero, 0, 0, 0);
         }
 
         public void ProcessMessage()
         {
-
             if (GetMessage(out var msg, IntPtr.Zero, 0, 0) > -1)
             {
                 TranslateMessage(ref msg);
@@ -222,8 +223,7 @@ namespace Avalonia.Win32
 
         public IDisposable StartTimer(DispatcherPriority priority, TimeSpan interval, Action callback)
         {
-            UnmanagedMethods.TimerProc timerDelegate =
+            TimerProc timerDelegate = (_, _, _, _) => callback();
-                (hWnd, uMsg, nIDEvent, dwTime) => callback();
 
             IntPtr handle = SetTimer(
                 IntPtr.Zero,
@@ -253,11 +253,11 @@ namespace Avalonia.Win32
                 new IntPtr(SignalL));
         }
 
-        public bool CurrentThreadIsLoopThread => _uiThread == Thread.CurrentThread;
+        public bool CurrentThreadIsLoopThread => s_uiThread == Thread.CurrentThread;
 
-        public event Action<DispatcherPriority?> Signaled;
+        public event Action<DispatcherPriority?>? Signaled;
 
-        public event EventHandler<ShutdownRequestedEventArgs> ShutdownRequested;
+        public event EventHandler<ShutdownRequestedEventArgs>? ShutdownRequested;
 
         [SuppressMessage("Microsoft.StyleCop.CSharp.NamingRules", "SA1305:FieldNamesMustNotUseHungarianNotation", Justification = "Using Win32 naming for consistency.")]
         private IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
@@ -301,11 +301,11 @@ namespace Avalonia.Win32
         private void CreateMessageWindow()
         {
             // Ensure that the delegate doesn't get garbage collected by storing it as a field.
-            _wndProcDelegate = new UnmanagedMethods.WndProc(WndProc);
+            _wndProcDelegate = WndProc;
 
-            UnmanagedMethods.WNDCLASSEX wndClassEx = new UnmanagedMethods.WNDCLASSEX
+            WNDCLASSEX wndClassEx = new WNDCLASSEX
             {
-                cbSize = Marshal.SizeOf<UnmanagedMethods.WNDCLASSEX>(),
+                cbSize = Marshal.SizeOf<WNDCLASSEX>(),
                 lpfnWndProc = _wndProcDelegate,
                 hInstance = GetModuleHandle(null),
                 lpszClassName = "AvaloniaMessageWindow " + Guid.NewGuid(),
@@ -326,7 +326,7 @@ namespace Avalonia.Win32
             }
         }
 
-        public ITrayIconImpl CreateTrayIcon ()
+        public ITrayIconImpl CreateTrayIcon()
         {
             return new TrayIconImpl();
         }

src/Windows/Avalonia.Win32/Win32PlatformSettings.cs

@@ -1,8 +1,6 @@
 using System;
-using System.Runtime.InteropServices;
 using Avalonia.Input;
 using Avalonia.Platform;
-using Avalonia.Win32.Interop;
 using Avalonia.Win32.WinRT;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
@@ -10,14 +8,14 @@ namespace Avalonia.Win32;
 
 internal class Win32PlatformSettings : DefaultPlatformSettings
 {
-    private PlatformColorValues _lastColorValues;
+    private PlatformColorValues? _lastColorValues;
 
     public override Size GetTapSize(PointerType type)
     {
         return type switch
         {
             PointerType.Touch => new(10, 10),
-            _ => new(GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CXDRAG), GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDRAG)),
+            _ => new(GetSystemMetrics(SystemMetric.SM_CXDRAG), GetSystemMetrics(SystemMetric.SM_CYDRAG)),
         };
     }
 
@@ -26,7 +24,7 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
         return type switch
         {
             PointerType.Touch => new(16, 16),
-            _ => new(GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CXDOUBLECLK), GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDOUBLECLK)),
+            _ => new(GetSystemMetrics(SystemMetric.SM_CXDOUBLECLK), GetSystemMetrics(SystemMetric.SM_CYDOUBLECLK)),
         };
     }
 

src/Windows/Avalonia.Win32/Win32StorageProvider.cs

@@ -1,13 +1,10 @@
-#nullable enable
+using System;
-
-using System;
 using System.Linq;
 using System.Collections.Generic;
 using System.IO;
 using System.ComponentModel;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
-using Avalonia.MicroCom;
 using Avalonia.Platform.Storage;
 using Avalonia.Platform.Storage.FileIO;
 using Avalonia.Win32.Interop;
@@ -146,7 +143,7 @@ namespace Avalonia.Win32
                         }
                     }
 
-                    var showResult = frm.Show(_windowImpl.Handle!.Handle);
+                    var showResult = frm.Show(_windowImpl.Handle.Handle);
 
                     if ((uint)showResult == (uint)UnmanagedMethods.HRESULT.E_CANCELLED)
                     {
@@ -188,7 +185,7 @@ namespace Avalonia.Win32
                     var message = new Win32Exception(ex.HResult).Message;
                     throw new COMException(message, ex);
                 }
-            })!;
+            });
         }
 
 
@@ -220,7 +217,6 @@ namespace Avalonia.Win32
             }
 
             var size = Marshal.SizeOf<UnmanagedMethods.COMDLG_FILTERSPEC>();
-            var arr = new byte[size];
             var resultArr = new byte[size * filters.Count];
 
             for (int i = 0; i < filters.Count; i++)
@@ -236,7 +232,7 @@ namespace Avalonia.Win32
                 {
                     var filterStr = new UnmanagedMethods.COMDLG_FILTERSPEC
                     {
-                        pszName = filter.Name ?? string.Empty,
+                        pszName = filter.Name,
                         pszSpec = string.Join(";", filter.Patterns)
                     };
 

src/Windows/Avalonia.Win32/WinRT/Composition/WinUIEffectBase.cs

@@ -1,14 +1,13 @@
 using System;
 using System.Linq;
 using System.Runtime.InteropServices;
-using Avalonia.MicroCom;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT.Composition
 {
-    abstract class WinUIEffectBase : WinRTInspectable, IGraphicsEffect,  IGraphicsEffectSource, IGraphicsEffectD2D1Interop
+    internal abstract class WinUIEffectBase : WinRTInspectable, IGraphicsEffect,  IGraphicsEffectSource, IGraphicsEffectD2D1Interop
     {
-        private IGraphicsEffectSource[] _sources;
+        private IGraphicsEffectSource[]? _sources;
 
         public WinUIEffectBase(params IGraphicsEffectSource[] _sources)
         {
@@ -32,7 +31,7 @@ namespace Avalonia.Win32.WinRT.Composition
             throw new COMException("Not supported", unchecked((int)0x80004001));
 
         public abstract uint PropertyCount { get; }
-        public abstract IPropertyValue GetProperty(uint index);
+        public abstract IPropertyValue? GetProperty(uint index);
 
         public IGraphicsEffectSource GetSource(uint index)
         {
@@ -53,14 +52,14 @@ namespace Avalonia.Win32.WinRT.Composition
             _sources = null;
         }
     }
-    
+
-    class WinUIGaussianBlurEffect : WinUIEffectBase
+    internal class WinUIGaussianBlurEffect : WinUIEffectBase
     {
         public WinUIGaussianBlurEffect(IGraphicsEffectSource source) : base(source)
         {
         }
 
-        enum D2D1_GAUSSIANBLUR_OPTIMIZATION
+        private enum D2D1_GAUSSIANBLUR_OPTIMIZATION
         {
             D2D1_GAUSSIANBLUR_OPTIMIZATION_SPEED,
             D2D1_GAUSSIANBLUR_OPTIMIZATION_BALANCED,
@@ -68,14 +67,14 @@ namespace Avalonia.Win32.WinRT.Composition
             D2D1_GAUSSIANBLUR_OPTIMIZATION_FORCE_DWORD
         };
 
-        enum D2D1_BORDER_MODE
+        private enum D2D1_BORDER_MODE
         {
             D2D1_BORDER_MODE_SOFT,
             D2D1_BORDER_MODE_HARD,
             D2D1_BORDER_MODE_FORCE_DWORD
         };
 
-        enum D2D1GaussianBlurProp
+        private enum D2D1GaussianBlurProp
         {
             D2D1_GAUSSIANBLUR_PROP_STANDARD_DEVIATION,
             D2D1_GAUSSIANBLUR_PROP_OPTIMIZATION,
@@ -87,7 +86,7 @@ namespace Avalonia.Win32.WinRT.Composition
 
         public override uint PropertyCount => 3;
 
-        public override IPropertyValue GetProperty(uint index)
+        public override IPropertyValue? GetProperty(uint index)
         {
             switch ((D2D1GaussianBlurProp)index)
             {
@@ -105,14 +104,14 @@ namespace Avalonia.Win32.WinRT.Composition
             return null;
         }
     }
-    
+
-    class SaturationEffect : WinUIEffectBase
+    internal class SaturationEffect : WinUIEffectBase
     {
         public SaturationEffect(IGraphicsEffectSource source) : base(source)
         {
         }
 
-        enum D2D1_SATURATION_PROP
+        private enum D2D1_SATURATION_PROP
         {
             D2D1_SATURATION_PROP_SATURATION,
             D2D1_SATURATION_PROP_FORCE_DWORD
@@ -122,7 +121,7 @@ namespace Avalonia.Win32.WinRT.Composition
 
         public override uint PropertyCount => 1;
 
-        public override IPropertyValue GetProperty(uint index)
+        public override IPropertyValue? GetProperty(uint index)
         {
             switch ((D2D1_SATURATION_PROP)index)
             {

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindow.cs

@@ -3,7 +3,6 @@ using System.Numerics;
 using System.Threading;
 using Avalonia.OpenGL.Egl;
 using Avalonia.Reactive;
-using Avalonia.Win32.Interop;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT.Composition;
@@ -12,8 +11,8 @@ internal class WinUiCompositedWindow : IDisposable
 {
     public EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo WindowInfo { get; }
     private readonly WinUiCompositionShared _shared;
-    private readonly ICompositionRoundedRectangleGeometry _compositionRoundedRectangleGeometry;
+    private readonly ICompositionRoundedRectangleGeometry? _compositionRoundedRectangleGeometry;
-    private readonly IVisual _mica;
+    private readonly IVisual? _mica;
     private readonly IVisual _blur;
     private readonly IVisual _visual;
     private PixelSize _size;
@@ -25,7 +24,7 @@ internal class WinUiCompositedWindow : IDisposable
         lock (_shared.SyncRoot)
         {
             _compositionRoundedRectangleGeometry?.Dispose();
-            _blur?.Dispose();
+            _blur.Dispose();
             _mica?.Dispose();
             _visual.Dispose();
             _surfaceBrush.Dispose();

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindowSurface.cs

@@ -1,15 +1,8 @@
 using System;
-using System.Runtime.InteropServices;
-using Avalonia.MicroCom;
-using Avalonia.OpenGL;
-using Avalonia.OpenGL.Angle;
 using Avalonia.OpenGL.Egl;
-using Avalonia.OpenGL.Surfaces;
 using Avalonia.Platform;
-using Avalonia.Utilities;
 using Avalonia.Win32.DirectX;
 using Avalonia.Win32.Interop;
-using Avalonia.Win32.OpenGl.Angle;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT.Composition
@@ -18,7 +11,7 @@ namespace Avalonia.Win32.WinRT.Composition
     {
         private readonly WinUiCompositionShared _shared;
         private readonly EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo _info;
-        private WinUiCompositedWindow _window;
+        private WinUiCompositedWindow? _window;
         private BlurEffect _blurEffect;
 
         public WinUiCompositedWindowSurface(WinUiCompositionShared shared, EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo info)
@@ -52,6 +45,8 @@ namespace Avalonia.Win32.WinRT.Composition
 
     internal class WinUiCompositedWindowRenderTarget : IDirect3D11TextureRenderTarget
     {
+        private static readonly Guid IID_ID3D11Texture2D = Guid.Parse("6f15aaf2-d208-4e89-9ab4-489535d34f9c");
+
         private readonly IPlatformGraphicsContext _context;
         private readonly WinUiCompositedWindow _window;
         private readonly IUnknown _d3dDevice;
@@ -63,6 +58,7 @@ namespace Avalonia.Win32.WinRT.Composition
         private PixelSize _size;
         private bool _lost;
         private readonly ICompositionDrawingSurfaceInterop _surfaceInterop;
+        private readonly ICompositionDrawingSurface _drawingSurface;
 
         public WinUiCompositedWindowRenderTarget(IPlatformGraphicsContext context,
             WinUiCompositedWindow window, IntPtr device,
@@ -83,28 +79,33 @@ namespace Avalonia.Win32.WinRT.Composition
                 _surface = _drawingSurface.QueryInterface<ICompositionSurface>();
                 _surfaceInterop = _drawingSurface.QueryInterface<ICompositionDrawingSurfaceInterop>();
             }
-            finally
+            catch
             {
-                if (_surfaceInterop == null)
+                _surface?.Dispose();
-                    Dispose();
+                _surfaceInterop?.Dispose();
+                _drawingSurface?.Dispose();
+                _compositionDevice2?.Dispose();
+                _compositionDevice?.Dispose();
+                _interop?.Dispose();
+                _compositor?.Dispose();
+                _d3dDevice?.Dispose();
+                throw;
             }
         }
 
         public void Dispose()
         {
-            _surface?.Dispose();
+            _surface.Dispose();
-            _surfaceInterop?.Dispose();
+            _surfaceInterop.Dispose();
-            _drawingSurface?.Dispose();
+            _drawingSurface.Dispose();
-            _compositionDevice2?.Dispose();
+            _compositionDevice2.Dispose();
-            _compositionDevice?.Dispose();
+            _compositionDevice.Dispose();
-            _interop?.Dispose();
+            _interop.Dispose();
-            _compositor?.Dispose();
+            _compositor.Dispose();
-            _d3dDevice?.Dispose();
+            _d3dDevice.Dispose();
         }
 
         public bool IsCorrupted => _context.IsLost || _lost;
-        private static Guid IID_ID3D11Texture2D = Guid.Parse("6f15aaf2-d208-4e89-9ab4-489535d34f9c");
-        private readonly ICompositionDrawingSurface _drawingSurface;
 
         public unsafe IDirect3D11TextureRenderTargetRenderSession BeginDraw()
         {
@@ -155,12 +156,12 @@ namespace Avalonia.Win32.WinRT.Composition
                 {
                     if (needsEndDraw)
                         _surfaceInterop.EndDraw();
-                    transaction?.Dispose();
+                    transaction.Dispose();
                 }
             }
         }
 
-        class Session : IDirect3D11TextureRenderTargetRenderSession
+        private class Session : IDirect3D11TextureRenderTargetRenderSession
         {
             private readonly IDisposable _transaction;
             private readonly PixelSize _size;
@@ -200,4 +201,4 @@ namespace Avalonia.Win32.WinRT.Composition
             public double Scaling => _scaling;
         }
     }
-}
+}

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositionShared.cs

@@ -8,11 +8,11 @@ internal class WinUiCompositionShared : IDisposable
     public ICompositor Compositor { get; }
     public ICompositor5 Compositor5 { get; }
     public ICompositorDesktopInterop DesktopInterop { get; }
-    public ICompositionBrush BlurBrush;
+    public ICompositionBrush BlurBrush { get; }
-    public ICompositionBrush MicaBrush;
+    public ICompositionBrush? MicaBrush { get; }
     public object SyncRoot { get; } = new();
 
-    public static readonly Version MinHostBackdropVersion = new Version(10, 0, 22000);
+    public static readonly Version MinHostBackdropVersion = new(10, 0, 22000);
     
     public WinUiCompositionShared(ICompositor compositor)
     {
@@ -26,9 +26,9 @@ internal class WinUiCompositionShared : IDisposable
     public void Dispose()
     {
         BlurBrush.Dispose();
-        MicaBrush.Dispose();
+        MicaBrush?.Dispose();
         DesktopInterop.Dispose();
         Compositor.Dispose();
         Compositor5.Dispose();
     }
-}
+}

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositionUtils.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Numerics;
 using MicroCom.Runtime;
 
@@ -6,7 +5,7 @@ namespace Avalonia.Win32.WinRT.Composition;
 
 internal static class WinUiCompositionUtils
 {
-    public static ICompositionBrush CreateMicaBackdropBrush(ICompositor compositor)
+    public static ICompositionBrush? CreateMicaBackdropBrush(ICompositor compositor)
     {
         if (Win32Platform.WindowsVersion.Build < 22000)
             return null;
@@ -18,7 +17,7 @@ internal static class WinUiCompositionUtils
         return blurredWallpaperBackdropBrush?.QueryInterface<ICompositionBrush>();
     }
 
-    public static unsafe ICompositionBrush CreateAcrylicBlurBackdropBrush(ICompositor compositor)
+    public static ICompositionBrush CreateAcrylicBlurBackdropBrush(ICompositor compositor)
     {
         using var backDropParameterFactory =
             NativeWinRTMethods.CreateActivationFactory<ICompositionEffectSourceParameterFactory>(
@@ -39,7 +38,7 @@ internal static class WinUiCompositionUtils
         return compositionEffectBrush.QueryInterface<ICompositionBrush>();
     }
 
-    public static ICompositionRoundedRectangleGeometry ClipVisual(ICompositor compositor, float? _backdropCornerRadius,  params IVisual[] containerVisuals)
+    public static ICompositionRoundedRectangleGeometry? ClipVisual(ICompositor compositor, float? _backdropCornerRadius,  params IVisual?[] containerVisuals)
     {
         if (!_backdropCornerRadius.HasValue)
             return null;
@@ -77,7 +76,7 @@ internal static class WinUiCompositionUtils
 
     public static ICompositionBrush CreateBackdropBrush(ICompositor compositor)
     {
-        ICompositionBackdropBrush brush = null;
+        ICompositionBackdropBrush? brush = null;
         try
         {
             if (Win32Platform.WindowsVersion >= WinUiCompositionShared.MinHostBackdropVersion)
@@ -98,4 +97,4 @@ internal static class WinUiCompositionUtils
             brush?.Dispose();
         }
     }
-}
+}

src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositorConnection.cs

@@ -7,20 +7,17 @@ using Avalonia.Logging;
 using Avalonia.MicroCom;
 using Avalonia.OpenGL.Egl;
 using Avalonia.Rendering;
-using Avalonia.Win32.DirectX;
 using Avalonia.Win32.Interop;
-using Avalonia.Win32.OpenGl.Angle;
-using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT.Composition;
 
 internal class WinUiCompositorConnection : IRenderTimer
 {
     private readonly WinUiCompositionShared _shared;
-    public event Action<TimeSpan> Tick;
+    public event Action<TimeSpan>? Tick;
     public bool RunsInBackground => true;
     
-    public unsafe WinUiCompositorConnection()
+    public WinUiCompositorConnection()
     {
         using var compositor = NativeWinRTMethods.CreateInstance<ICompositor>("Windows.UI.Composition.Compositor");
         /*
@@ -42,10 +39,9 @@ internal class WinUiCompositorConnection : IRenderTimer
         _shared = new WinUiCompositionShared(compositor);
     }
 
-    static bool TryCreateAndRegisterCore()
+    private static bool TryCreateAndRegisterCore()
     {
         var tcs = new TaskCompletionSource<bool>();
-        var pumpLock = new object();
         var th = new Thread(() =>
         {
             WinUiCompositorConnection connect;
@@ -80,10 +76,10 @@ internal class WinUiCompositorConnection : IRenderTimer
         return tcs.Task.Result;
     }
 
-    class RunLoopHandler : CallbackBase, IAsyncActionCompletedHandler 
+    private class RunLoopHandler : CallbackBase, IAsyncActionCompletedHandler
     {
         private readonly WinUiCompositorConnection _parent;
-        private Stopwatch _st = Stopwatch.StartNew();
+        private readonly Stopwatch _st = Stopwatch.StartNew();
 
         public RunLoopHandler(WinUiCompositorConnection parent)
         {
@@ -101,7 +97,7 @@ internal class WinUiCompositorConnection : IRenderTimer
     private void RunLoop()
     {
         var cts = new CancellationTokenSource();
-        AppDomain.CurrentDomain.ProcessExit += (sender, args) =>
+        AppDomain.CurrentDomain.ProcessExit += (_, _) =>
             cts.Cancel();
 
         lock (_shared.SyncRoot)

src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs

@@ -1,12 +1,6 @@
 using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.IO;
-using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Threading;
-using Avalonia.MicroCom;
-using Avalonia.Win32.Interop;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT
@@ -108,24 +102,24 @@ namespace Avalonia.Win32.WinRT
         [DllImport("combase.dll", PreserveSig = false)]
         private static extern IntPtr RoGetActivationFactory(IntPtr activatableClassId, ref Guid iid);
         
-        private static bool _initialized;
+        private static bool s_initialized;
         private static void EnsureRoInitialized()
         {
-            if (_initialized)
+            if (s_initialized)
                 return;
             RoInitialize(Thread.CurrentThread.GetApartmentState() == ApartmentState.STA ?
                 RO_INIT_TYPE.RO_INIT_SINGLETHREADED :
                 RO_INIT_TYPE.RO_INIT_MULTITHREADED);
-            _initialized = true;
+            s_initialized = true;
         }
     }
 
-    class HStringInterop : IDisposable
+    internal class HStringInterop : IDisposable
     {
         private IntPtr _s;
-        private bool _owns;
+        private readonly bool _owns;
 
-        public HStringInterop(string s)
+        public HStringInterop(string? s)
         {
             _s = s == null ? IntPtr.Zero : NativeWinRTMethods.WindowsCreateString(s);
             _owns = true;
@@ -139,7 +133,7 @@ namespace Avalonia.Win32.WinRT
 
         public IntPtr Handle => _s;
 
-        public unsafe string Value
+        public unsafe string? Value
         {
             get
             {

src/Windows/Avalonia.Win32/WinRT/WinRTInspectable.cs

@@ -2,12 +2,11 @@
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using Avalonia.MicroCom;
 using MicroCom.Runtime;
 
 namespace Avalonia.Win32.WinRT
 {
-    class WinRTInspectable : IInspectable, IMicroComShadowContainer
+    internal class WinRTInspectable : IInspectable, IMicroComShadowContainer
     {
         public virtual void Dispose()
         {
@@ -25,9 +24,9 @@ namespace Avalonia.Win32.WinRT
             *iidCount = (ulong) interfaces.Length;
         }
 
-        public IntPtr RuntimeClassName => NativeWinRTMethods.WindowsCreateString(GetType().FullName);
+        public IntPtr RuntimeClassName => NativeWinRTMethods.WindowsCreateString(GetType().FullName!);
         public TrustLevel TrustLevel => TrustLevel.BaseTrust;
-        public MicroComShadow Shadow { get; set; }
+        public MicroComShadow? Shadow { get; set; }
         public virtual void OnReferencedFromNative()
         {
         }

src/Windows/Avalonia.Win32/WinScreen.cs

@@ -15,14 +15,16 @@ namespace Avalonia.Win32
 
         public IntPtr Handle => _hMonitor;
 
+        /// <inheritdoc />
         public override int GetHashCode()
         {
-            return (int)_hMonitor;
+            return _hMonitor.GetHashCode();
         }
 
-        public override bool Equals(object obj)
+        /// <inheritdoc />
+        public override bool Equals(object? obj)
         {
-            return (obj is WinScreen screen) ? _hMonitor == screen._hMonitor : base.Equals(obj);
+            return obj is WinScreen screen && _hMonitor == screen._hMonitor;
         }
     }
 }

src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs

@@ -1,12 +1,9 @@
 using System;
-using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
-using System.Text;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls;
-using Avalonia.Controls.Remote;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
 using Avalonia.Platform;
@@ -27,9 +24,9 @@ namespace Avalonia.Win32
         protected virtual unsafe IntPtr AppWndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
         {
             const double wheelDelta = 120.0;
-            const long UiaRootObjectId = -25;
+            const long uiaRootObjectId = -25;
             uint timestamp = unchecked((uint)GetMessageTime());
-            RawInputEventArgs e = null;
+            RawInputEventArgs? e = null;
             var shouldTakeFocus = false;
             var message = (WindowsMessage)msg;
             switch (message)
@@ -92,7 +89,7 @@ namespace Avalonia.Win32
                         }
 
                         // We need to release IMM context and state to avoid leaks.
-                        if (Imm32InputMethod.Current.HWND == _hwnd)
+                        if (Imm32InputMethod.Current.Hwnd == _hwnd)
                         {
                             Imm32InputMethod.Current.ClearLanguageAndWindow();
                         }
@@ -104,7 +101,7 @@ namespace Avalonia.Win32
                         Closed?.Invoke();
 
                         _mouseDevice.Dispose();
-                        _touchDevice?.Dispose();
+                        _touchDevice.Dispose();
                         //Free other resources
                         Dispose();
 
@@ -140,7 +137,7 @@ namespace Avalonia.Win32
                     {
                         var key = KeyInterop.KeyFromVirtualKey(ToInt32(wParam), ToInt32(lParam));
 
-                        if (key != Key.None)
+                        if (key != Key.None && _owner is not null)
                         {
                             e = new RawKeyEventArgs(
                                 WindowsKeyboardDevice.Instance,
@@ -170,7 +167,7 @@ namespace Avalonia.Win32
                     {
                         var key = KeyInterop.KeyFromVirtualKey(ToInt32(wParam), ToInt32(lParam));
 
-                        if (key != Key.None)
+                        if (key != Key.None && _owner is not null)
                         {
                             e = new RawKeyEventArgs(
                             WindowsKeyboardDevice.Instance,
@@ -185,7 +182,7 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_CHAR:
                     {
                         // Ignore control chars and chars that were handled in WM_KEYDOWN.
-                        if (ToInt32(wParam) >= 32 && !_ignoreWmChar)
+                        if (ToInt32(wParam) >= 32 && !_ignoreWmChar && _owner is not null)
                         {
                             e = new RawTextInputEventArgs(WindowsKeyboardDevice.Instance, timestamp, _owner,
                                 new string((char)ToInt32(wParam), 1));
@@ -204,7 +201,7 @@ namespace Avalonia.Win32
                             break;
                         }
                         shouldTakeFocus = ShouldTakeFocusOnClick;
-                        if (ShouldIgnoreTouchEmulatedMessage())
+                        if (ShouldIgnoreTouchEmulatedMessage() || _owner is null)
                         {
                             break;
                         }
@@ -213,7 +210,9 @@ namespace Avalonia.Win32
                             _mouseDevice,
                             timestamp,
                             _owner,
+#pragma warning disable CS8509
                             message switch
+#pragma warning restore CS8509
                             {
                                 WindowsMessage.WM_LBUTTONDOWN => RawPointerEventType.LeftButtonDown,
                                 WindowsMessage.WM_RBUTTONDOWN => RawPointerEventType.RightButtonDown,
@@ -221,7 +220,7 @@ namespace Avalonia.Win32
                                 WindowsMessage.WM_XBUTTONDOWN =>
                                 HighWord(ToInt32(wParam)) == 1 ?
                                     RawPointerEventType.XButton1Down :
-                                    RawPointerEventType.XButton2Down
+                                    RawPointerEventType.XButton2Down,
                             },
                             DipFromLParam(lParam), GetMouseModifiers(wParam));
                         break;
@@ -236,7 +235,7 @@ namespace Avalonia.Win32
                         {
                             break;
                         }
-                        if (ShouldIgnoreTouchEmulatedMessage())
+                        if (ShouldIgnoreTouchEmulatedMessage() || _owner is null)
                         {
                             break;
                         }
@@ -245,7 +244,9 @@ namespace Avalonia.Win32
                             _mouseDevice,
                             timestamp,
                             _owner,
+#pragma warning disable CS8509
                             message switch
+#pragma warning restore CS8509
                             {
                                 WindowsMessage.WM_LBUTTONUP => RawPointerEventType.LeftButtonUp,
                                 WindowsMessage.WM_RBUTTONUP => RawPointerEventType.RightButtonUp,
@@ -309,6 +310,11 @@ namespace Avalonia.Win32
                         var prevPoint = _lastWmMousePoint;
                         _lastWmMousePoint = currPoint;
 
+                        if (_owner is null)
+                        {
+                            break;
+                        }
+
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
@@ -317,7 +323,7 @@ namespace Avalonia.Win32
                             point,
                             GetMouseModifiers(wParam))
                         {
-                            IntermediatePoints = new Lazy<IReadOnlyList<RawPointerPoint>>(() => CreateLazyIntermediatePoints(currPoint, prevPoint))
+                            IntermediatePoints = new Lazy<IReadOnlyList<RawPointerPoint>?>(() => CreateIntermediatePoints(currPoint, prevPoint))
                         };
 
                         break;
@@ -325,7 +331,7 @@ namespace Avalonia.Win32
 
                 case WindowsMessage.WM_MOUSEWHEEL:
                     {
-                        if (IsMouseInPointerEnabled)
+                        if (IsMouseInPointerEnabled || _owner is null)
                         {
                             break;
                         }
@@ -341,7 +347,7 @@ namespace Avalonia.Win32
 
                 case WindowsMessage.WM_MOUSEHWHEEL:
                     {
-                        if (IsMouseInPointerEnabled)
+                        if (IsMouseInPointerEnabled || _owner is null)
                         {
                             break;
                         }
@@ -362,6 +368,10 @@ namespace Avalonia.Win32
                             break;
                         }
                         _trackingMouse = false;
+                        if (_owner is null)
+                        {
+                            break;
+                        }
                         e = new RawPointerEventArgs(
                             _mouseDevice,
                             timestamp,
@@ -377,7 +387,7 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_NCMBUTTONDOWN:
                 case WindowsMessage.WM_NCXBUTTONDOWN:
                     {
-                        if (IsMouseInPointerEnabled)
+                        if (IsMouseInPointerEnabled || _owner is null)
                         {
                             break;
                         }
@@ -385,7 +395,9 @@ namespace Avalonia.Win32
                             _mouseDevice,
                             timestamp,
                             _owner,
+#pragma warning disable CS8509
                             message switch
+#pragma warning restore CS8509
                             {
                                 WindowsMessage.WM_NCLBUTTONDOWN => RawPointerEventType
                                     .NonClientLeftButtonDown,
@@ -396,12 +408,12 @@ namespace Avalonia.Win32
                                     RawPointerEventType.XButton1Down :
                                     RawPointerEventType.XButton2Down,
                             },
-                            PointToClient(WindowImpl.PointFromLParam(lParam)), GetMouseModifiers(wParam));
+                            PointToClient(PointFromLParam(lParam)), GetMouseModifiers(wParam));
                         break;
                     }
                 case WindowsMessage.WM_TOUCH:
                     {
-                        if (_wmPointerEnabled)
+                        if (_wmPointerEnabled || _owner is null || Input is not { } input)
                         {
                             break;
                         }
@@ -414,7 +426,7 @@ namespace Avalonia.Win32
                         {
                             foreach (var touchInput in touchInputs)
                             {
-                                Input?.Invoke(new RawTouchEventArgs(_touchDevice, touchInput.Time,
+                                input.Invoke(new RawTouchEventArgs(_touchDevice, touchInput.Time,
                                     _owner,
                                     touchInput.Flags.HasAllFlags(TouchInputFlags.TOUCHEVENTF_UP) ?
                                         RawPointerEventType.TouchEnd :
@@ -438,14 +450,14 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_POINTERUP:
                 case WindowsMessage.WM_POINTERUPDATE:
                     {
-                        if (!_wmPointerEnabled)
+                        if (!_wmPointerEnabled || _owner is null)
                         {
                             break;
                         }
                         GetDevicePointerInfo(wParam, out var device, out var info, out var point, out var modifiers, ref timestamp);
                         var eventType = GetEventType(message, info);
 
-                        var args = CreatePointerArgs(device, timestamp, eventType, point, modifiers, info.pointerId);
+                        var args = CreatePointerArgs(device, timestamp, _owner, eventType, point, modifiers, info.pointerId);
                         args.IntermediatePoints = CreateLazyIntermediatePoints(info);
                         e = args;
                         break;
@@ -454,19 +466,19 @@ namespace Avalonia.Win32
                 case WindowsMessage.WM_POINTERLEAVE:
                 case WindowsMessage.WM_POINTERCAPTURECHANGED:
                     {
-                        if (!_wmPointerEnabled)
+                        if (!_wmPointerEnabled || _owner is null)
                         {
                             break;
                         }
                         GetDevicePointerInfo(wParam, out var device, out var info, out var point, out var modifiers, ref timestamp);
                         var eventType = device is TouchDevice ? RawPointerEventType.TouchCancel : RawPointerEventType.LeaveWindow;
-                        e = CreatePointerArgs(device, timestamp, eventType, point, modifiers, info.pointerId);
+                        e = CreatePointerArgs(device, timestamp, _owner, eventType, point, modifiers, info.pointerId);
                         break;
                     }
                 case WindowsMessage.WM_POINTERWHEEL:
                 case WindowsMessage.WM_POINTERHWHEEL:
                     {
-                        if (!_wmPointerEnabled)
+                        if (!_wmPointerEnabled || _owner is null)
                         {
                             break;
                         }
@@ -488,7 +500,7 @@ namespace Avalonia.Win32
                         }
 
                         // Do not generate events, but release mouse capture on any other device input.
-                        GetDevicePointerInfo(wParam, out var device, out var info, out var point, out var modifiers, ref timestamp);
+                        GetDevicePointerInfo(wParam, out var device, out _, out _, out _, ref timestamp);
                         if (device != _mouseDevice)
                         {
                             _mouseDevice.Capture(null);
@@ -726,9 +738,9 @@ namespace Avalonia.Win32
                     break;
 
                 case WindowsMessage.WM_GETOBJECT:
-                    if ((long)lParam == UiaRootObjectId && UiaCoreTypesApi.IsNetComInteropAvailable)
+                    if ((long)lParam == uiaRootObjectId && UiaCoreTypesApi.IsNetComInteropAvailable && _owner is Control control)
                     {
-                        var peer = ControlAutomationPeer.CreatePeerForElement((Control)_owner);
+                        var peer = ControlAutomationPeer.CreatePeerForElement(control);
                         var node = AutomationNode.GetOrCreate(peer);
                         return UiaCoreProviderApi.UiaReturnRawElementProvider(_hwnd, wParam, lParam, node);
                     }
@@ -775,12 +787,12 @@ namespace Avalonia.Win32
             }
         }
 
-        private unsafe Lazy<IReadOnlyList<RawPointerPoint>> CreateLazyIntermediatePoints(POINTER_INFO info)
+        private Lazy<IReadOnlyList<RawPointerPoint>?>? CreateLazyIntermediatePoints(POINTER_INFO info)
         {
             var historyCount = Math.Min((int)info.historyCount, MaxPointerHistorySize);
             if (historyCount > 1)
             {
-                return new Lazy<IReadOnlyList<RawPointerPoint>>(() =>
+                return new Lazy<IReadOnlyList<RawPointerPoint>?>(() =>
                 {
                     s_intermediatePointsPooledList.Clear();
                     s_intermediatePointsPooledList.Capacity = historyCount;
@@ -829,7 +841,7 @@ namespace Avalonia.Win32
             return null;
         }
 
-        private unsafe IReadOnlyList<RawPointerPoint> CreateLazyIntermediatePoints(MOUSEMOVEPOINT movePoint, MOUSEMOVEPOINT prevMovePoint)
+        private unsafe IReadOnlyList<RawPointerPoint> CreateIntermediatePoints(MOUSEMOVEPOINT movePoint, MOUSEMOVEPOINT prevMovePoint)
         {
             // To understand some of this code, please check MS docs:
             // https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getmousemovepointsex#remarks
@@ -888,11 +900,11 @@ namespace Avalonia.Win32
             }
         }
 
-        private RawPointerEventArgs CreatePointerArgs(IInputDevice device, ulong timestamp, RawPointerEventType eventType, RawPointerPoint point, RawInputModifiers modifiers, uint rawPointerId)
+        private RawPointerEventArgs CreatePointerArgs(IInputDevice device, ulong timestamp, IInputRoot owner, RawPointerEventType eventType, RawPointerPoint point, RawInputModifiers modifiers, uint rawPointerId)
         {
             return device is TouchDevice
-                ? new RawTouchEventArgs(device, timestamp, _owner, eventType, point, modifiers, rawPointerId)
+                ? new RawTouchEventArgs(device, timestamp, owner, eventType, point, modifiers, rawPointerId)
-                : new RawPointerEventArgs(device, timestamp, _owner, eventType, point, modifiers)
+                : new RawPointerEventArgs(device, timestamp, owner, eventType, point, modifiers)
                 {
                     RawPointerId = rawPointerId
                 };
@@ -1029,7 +1041,7 @@ namespace Avalonia.Win32
             // note: for non-ime language, also create it so that emoji panel tracks cursor
             var langid = LGID(hkl);
 
-            if (langid == _langid && Imm32InputMethod.Current.HWND == Hwnd)
+            if (langid == _langid && Imm32InputMethod.Current.Hwnd == Hwnd)
             {
                 return;
             }

src/Windows/Avalonia.Win32/WindowImpl.CustomCaptionProc.cs

@@ -3,8 +3,6 @@ using Avalonia.Controls;
 using Avalonia.Input;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
-#nullable enable
-
 namespace Avalonia.Win32
 {
     public partial class WindowImpl
@@ -13,7 +11,7 @@ namespace Avalonia.Win32
         private HitTestValues HitTestNCA(IntPtr hWnd, IntPtr wParam, IntPtr lParam)
         {
             // Get the point coordinates for the hit test (screen space).
-            var ptMouse = WindowImpl.PointFromLParam(lParam);
+            var ptMouse = PointFromLParam(lParam);
 
             // Get the window rectangle.
             GetWindowRect(hWnd, out var rcWindow);
@@ -101,11 +99,9 @@ namespace Avalonia.Win32
 
                         lRet = (IntPtr)hittestResult;
 
-                        uint timestamp = unchecked((uint)GetMessageTime());
-
                         if (hittestResult == HitTestValues.HTCAPTION)
                         {
-                            var position = PointToClient(WindowImpl.PointFromLParam(lParam));
+                            var position = PointToClient(PointFromLParam(lParam));
 
                             if (_owner is Window window)
                             {

src/Windows/Avalonia.Win32/WindowImpl.WndProc.cs

@@ -2,14 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
-using System.Diagnostics.CodeAnalysis;
-using System.Runtime.InteropServices;
-using Avalonia.Controls;
 using Avalonia.Controls.Platform;
-using Avalonia.Input;
-using Avalonia.Input.Raw;
-using Avalonia.Win32.Input;
-using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia.Win32
 {

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -1,33 +1,29 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.InteropServices;
-using Avalonia.Controls;
+using Avalonia.Collections.Pooled;
-using Avalonia.Automation.Peers;
 using Avalonia.Controls.Platform;
-using Avalonia.Input;
+using Avalonia.Controls;
 using Avalonia.Input.Raw;
 using Avalonia.Input.TextInput;
-using Avalonia.OpenGL;
+using Avalonia.Input;
-using Avalonia.OpenGL.Angle;
+using Avalonia.Metadata;
 using Avalonia.OpenGL.Egl;
-using Avalonia.OpenGL.Surfaces;
+using Avalonia.Platform.Storage;
 using Avalonia.Platform;
-using Avalonia.Rendering;
 using Avalonia.Rendering.Composition;
-using Avalonia.Win32.Automation;
+using Avalonia.Rendering;
+using Avalonia.Win32.DirectX;
 using Avalonia.Win32.Input;
 using Avalonia.Win32.Interop;
+using Avalonia.Win32.OpenGl.Angle;
 using Avalonia.Win32.OpenGl;
-using Avalonia.Win32.WinRT;
 using Avalonia.Win32.WinRT.Composition;
+using Avalonia.Win32.WinRT;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
-using Avalonia.Collections.Pooled;
-using Avalonia.Metadata;
-using Avalonia.Platform.Storage;
-using Avalonia.Win32.DirectX;
-using Avalonia.Win32.OpenGl.Angle;
 
 namespace Avalonia.Win32
 {
@@ -37,13 +33,13 @@ namespace Avalonia.Win32
     [Unstable]
     public partial class WindowImpl : IWindowImpl, EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo
     {
-        private static readonly List<WindowImpl> s_instances = new List<WindowImpl>();
+        private static readonly List<WindowImpl> s_instances = new();
 
-        private static readonly IntPtr DefaultCursor = LoadCursor(
+        private static readonly IntPtr s_defaultCursor = LoadCursor(
             IntPtr.Zero, new IntPtr((int)UnmanagedMethods.Cursor.IDC_ARROW));
 
         private static readonly Dictionary<WindowEdge, HitTestValues> s_edgeLookup =
-            new Dictionary<WindowEdge, HitTestValues>
+            new()
             {
                 { WindowEdge.East, HitTestValues.HTRIGHT },
                 { WindowEdge.North, HitTestValues.HTTOP },
@@ -61,8 +57,8 @@ namespace Avalonia.Win32
         private Thickness _extendedMargins;
         private Thickness _offScreenMargin;
         private double _extendTitleBarHint = -1;
-        private bool _isUsingComposition;
+        private readonly bool _isUsingComposition;
-        private IBlurHost _blurHost;
+        private readonly IBlurHost? _blurHost;
         private PlatformResizeReason _resizeReason;
         private MOUSEMOVEPOINT _lastWmMousePoint;
 
@@ -76,26 +72,26 @@ namespace Avalonia.Win32
         private readonly PenDevice _penDevice;
         private readonly ManagedDeferredRendererLock _rendererLock;
         private readonly FramebufferManager _framebuffer;
-        private readonly object _gl;
+        private readonly object? _gl;
         private readonly bool _wmPointerEnabled;
 
-        private Win32NativeControlHost _nativeControlHost;
+        private readonly Win32NativeControlHost _nativeControlHost;
-        private IStorageProvider _storageProvider;
+        private readonly IStorageProvider _storageProvider;
         private WndProc _wndProcDelegate;
-        private string _className;
+        private string? _className;
         private IntPtr _hwnd;
-        private IInputRoot _owner;
+        private IInputRoot? _owner;
         private WindowProperties _windowProperties;
         private bool _trackingMouse;//ToDo - there is something missed. Needs investigation @Steven Kirk
         private bool _topmost;
         private double _scaling = 1;
         private WindowState _showWindowState;
         private WindowState _lastWindowState;
-        private OleDropTarget _dropTarget;
+        private OleDropTarget? _dropTarget;
         private Size _minSize;
         private Size _maxSize;
         private POINT _maxTrackSize;
-        private WindowImpl _parent;
+        private WindowImpl? _parent;
         private ExtendClientAreaChromeHints _extendChromeHints = ExtendClientAreaChromeHints.Default;
         private bool _isCloseRequested;
         private bool _shown;
@@ -142,7 +138,7 @@ namespace Avalonia.Win32
                           angle.PlatformApi == AngleOptions.PlatformApi.DirectX11;
             _isUsingComposition = compositionConnector is { } && isUsingAngleDX11;
 
-            DxgiConnection dxgiConnection = null;
+            DxgiConnection? dxgiConnection = null;
             var isUsingDxgiSwapchain = false;
             if (!_isUsingComposition)
             {
@@ -159,23 +155,20 @@ namespace Avalonia.Win32
             {
                 if (_isUsingComposition)
                 {
-                    var cgl = compositionConnector.CreateSurface(this);
+                    var cgl = compositionConnector!.CreateSurface(this);
                     _blurHost = cgl;
-
                     _gl = cgl;
-
-                    _isUsingComposition = true;
                 }
                 else if (isUsingDxgiSwapchain)
                 {
-                    var dxgigl = new DxgiSwapchainWindow(dxgiConnection, this);
+                    var dxgigl = new DxgiSwapchainWindow(dxgiConnection!, this);
                     _gl = dxgigl;
                 }
                 else
                 {
-                    if (glPlatform is AngleWin32PlatformGraphics egl2)
+                    if (glPlatform is AngleWin32PlatformGraphics)
                         _gl = new EglGlPlatformSurface(this);
-                    else if (glPlatform is WglPlatformOpenGlInterface wgl)
+                    else if (glPlatform is WglPlatformOpenGlInterface)
                         _gl = new WglGlPlatformSurface(this);
                 }
             }
@@ -187,29 +180,41 @@ namespace Avalonia.Win32
             s_instances.Add(this);
         }
 
-        public Action Activated { get; set; }
+        /// <inheritdoc />
+        public Action? Activated { get; set; }
 
-        public Func<WindowCloseReason, bool> Closing { get; set; }
+        /// <inheritdoc />
+        public Func<WindowCloseReason, bool>? Closing { get; set; }
 
-        public Action Closed { get; set; }
+        /// <inheritdoc />
+        public Action? Closed { get; set; }
 
-        public Action Deactivated { get; set; }
+        /// <inheritdoc />
+        public Action? Deactivated { get; set; }
 
-        public Action<RawInputEventArgs> Input { get; set; }
+        /// <inheritdoc />
+        public Action<RawInputEventArgs>? Input { get; set; }
 
-        public Action<Rect> Paint { get; set; }
+        /// <inheritdoc />
+        public Action<Rect>? Paint { get; set; }
 
-        public Action<Size, PlatformResizeReason> Resized { get; set; }
+        /// <inheritdoc />
+        public Action<Size, PlatformResizeReason>? Resized { get; set; }
 
-        public Action<double> ScalingChanged { get; set; }
+        /// <inheritdoc />
+        public Action<double>? ScalingChanged { get; set; }
 
-        public Action<PixelPoint> PositionChanged { get; set; }
+        /// <inheritdoc />
+        public Action<PixelPoint>? PositionChanged { get; set; }
 
-        public Action<WindowState> WindowStateChanged { get; set; }
+        /// <inheritdoc />
+        public Action<WindowState>? WindowStateChanged { get; set; }
 
-        public Action LostFocus { get; set; }
+        /// <inheritdoc />
+        public Action? LostFocus { get; set; }
 
-        public Action<WindowTransparencyLevel> TransparencyLevelChanged { get; set; }
+        /// <inheritdoc />
+        public Action<WindowTransparencyLevel>? TransparencyLevelChanged { get; set; }
 
         public Thickness BorderThickness
         {
@@ -240,10 +245,13 @@ namespace Avalonia.Win32
 
         private double PrimaryScreenRenderScaling => Screen.AllScreens.FirstOrDefault(screen => screen.IsPrimary)?.Scaling ?? 1;
 
+        /// <inheritdoc />
         public double RenderScaling => _scaling;
 
+        /// <inheritdoc />
         public double DesktopScaling => RenderScaling;
 
+        /// <inheritdoc />
         public Size ClientSize
         {
             get
@@ -254,6 +262,7 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public Size? FrameSize
         {
             get
@@ -269,14 +278,18 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public IScreenImpl Screen { get; }
 
+        /// <inheritdoc />
         public IPlatformHandle Handle { get; private set; }
 
+        /// <inheritdoc />
         public virtual Size MaxAutoSizeHint => new Size(_maxTrackSize.X / RenderScaling, _maxTrackSize.Y / RenderScaling);
 
         public IMouseDevice MouseDevice => _mouseDevice;
 
+        /// <inheritdoc />
         public WindowState WindowState
         {
             get
@@ -314,13 +327,15 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
 
         protected IntPtr Hwnd => _hwnd;
 
         private bool IsMouseInPointerEnabled => _wmPointerEnabled && IsMouseInPointerEnabled();
 
-        public object TryGetFeature(Type featureType)
+        /// <inheritdoc />
+        public object? TryGetFeature(Type featureType)
         {
             if (featureType == typeof(ITextInputMethodImpl))
             {
@@ -339,7 +354,8 @@ namespace Avalonia.Win32
 
             return null;
         }
-        
+
+        /// <inheritdoc />
         public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
         {
             TransparencyLevel = EnableBlur(transparencyLevel);
@@ -521,8 +537,13 @@ namespace Avalonia.Win32
             }
         }
 
-        public IEnumerable<object> Surfaces => new object[] { (IPlatformNativeSurfaceHandle)Handle, _gl, _framebuffer };
+        /// <inheritdoc />
+        public IEnumerable<object> Surfaces
+            => _gl is null ?
+                new object[] { Handle, _framebuffer } :
+                new object[] { Handle, _gl, _framebuffer };
 
+        /// <inheritdoc />
         public PixelPoint Position
         {
             get
@@ -568,17 +589,21 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public void Move(PixelPoint point) => Position = point;
 
+        /// <inheritdoc />
         public void SetMinMaxSize(Size minSize, Size maxSize)
         {
             _minSize = minSize;
             _maxSize = maxSize;
         }
 
+        /// <inheritdoc />
         public IRenderer CreateRenderer(IRenderRoot root) =>
             new CompositingRenderer(root, Win32Platform.Compositor, () => Surfaces);
 
+        /// <inheritdoc />
         public void Resize(Size value, PlatformResizeReason reason)
         {
             if (WindowState != WindowState.Normal)
@@ -606,13 +631,16 @@ namespace Avalonia.Win32
             }
         }
 
+        /// <inheritdoc />
         public void Activate()
         {
             SetForegroundWindow(_hwnd);
         }
 
-        public IPopupImpl CreatePopup() => Win32Platform.UseOverlayPopups ? null : new PopupImpl(this);
+        /// <inheritdoc />
+        public IPopupImpl? CreatePopup() => Win32Platform.UseOverlayPopups ? null : new PopupImpl(this);
 
+        /// <inheritdoc />
         public void Dispose()
         {
             (_gl as IDisposable)?.Dispose();
@@ -654,6 +682,7 @@ namespace Avalonia.Win32
             InvalidateRect(_hwnd, ref r, false);
         }
 
+        /// <inheritdoc />
         public Point PointToClient(PixelPoint point)
         {
             var p = new POINT { X = point.X, Y = point.Y };
@@ -661,6 +690,7 @@ namespace Avalonia.Win32
             return new Point(p.X, p.Y) / RenderScaling;
         }
 
+        /// <inheritdoc />
         public PixelPoint PointToScreen(Point point)
         {
             point *= RenderScaling;
@@ -669,29 +699,34 @@ namespace Avalonia.Win32
             return new PixelPoint(p.X, p.Y);
         }
 
+        /// <inheritdoc />
         public void SetInputRoot(IInputRoot inputRoot)
         {
             _owner = inputRoot;
-            CreateDropTarget();
+            CreateDropTarget(inputRoot);
         }
 
+        /// <inheritdoc />
         public void Hide()
         {
             UnmanagedMethods.ShowWindow(_hwnd, ShowWindowCommand.Hide);
             _shown = false;
         }
 
+        /// <inheritdoc />
         public virtual void Show(bool activate, bool isDialog)
         {
             SetParent(_parent);
             ShowWindow(_showWindowState, activate);
         }
 
-        public Action GotInputWhenDisabled { get; set; }
+        /// <inheritdoc />
+        public Action? GotInputWhenDisabled { get; set; }
 
-        public void SetParent(IWindowImpl parent)
+        /// <inheritdoc />
+        public void SetParent(IWindowImpl? parent)
         {
-            _parent = (WindowImpl)parent;
+            _parent = parent as WindowImpl;
 
             var parentHwnd = _parent?._hwnd ?? IntPtr.Zero;
 
@@ -704,8 +739,10 @@ namespace Avalonia.Win32
             SetWindowLongPtr(_hwnd, (int)WindowLongParam.GWL_HWNDPARENT, parentHwnd);
         }
 
+        /// <inheritdoc />
         public void SetEnabled(bool enable) => EnableWindow(_hwnd, enable);
 
+        /// <inheritdoc />
         public void BeginMoveDrag(PointerPressedEventArgs e)
         {
             e.Pointer.Capture(null);
@@ -713,6 +750,7 @@ namespace Avalonia.Win32
                 new IntPtr((int)HitTestValues.HTCAPTION), IntPtr.Zero);
         }
 
+        /// <inheritdoc />
         public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e)
         {
             if (_windowProperties.IsResizable)
@@ -727,35 +765,37 @@ namespace Avalonia.Win32
             }
         }
 
-        public void SetTitle(string title)
+        /// <inheritdoc />
+        public void SetTitle(string? title)
         {
             SetWindowText(_hwnd, title);
         }
 
-        public void SetCursor(ICursorImpl cursor)
+        /// <inheritdoc />
+        public void SetCursor(ICursorImpl? cursor)
         {
             var impl = cursor as CursorImpl;
 
-            if (cursor is null || impl is object)
+            var hCursor = impl?.Handle ?? s_defaultCursor;
-            {
+            SetClassLong(_hwnd, ClassLongIndex.GCLP_HCURSOR, hCursor);
-                var hCursor = impl?.Handle ?? DefaultCursor;
-                SetClassLong(_hwnd, ClassLongIndex.GCLP_HCURSOR, hCursor);
 
-                if (_owner.IsPointerOver)
+            if (_owner?.IsPointerOver == true)
-                {
+            {
-                    UnmanagedMethods.SetCursor(hCursor);
+                UnmanagedMethods.SetCursor(hCursor);
-                }
             }
         }
 
-        public void SetIcon(IWindowIconImpl icon)
+        /// <inheritdoc />
+        public void SetIcon(IWindowIconImpl? icon)
         {
-            var impl = (IconImpl)icon;
+            var impl = icon as IconImpl;
+
             var hIcon = impl?.HIcon ?? IntPtr.Zero;
             PostMessage(_hwnd, (int)WindowsMessage.WM_SETICON,
                 new IntPtr((int)Icons.ICON_BIG), hIcon);
         }
 
+        /// <inheritdoc />
         public void ShowTaskbarIcon(bool value)
         {
             var newWindowProperties = _windowProperties;
@@ -765,6 +805,7 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
+        /// <inheritdoc />
         public void CanResize(bool value)
         {
             var newWindowProperties = _windowProperties;
@@ -774,6 +815,7 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
+        /// <inheritdoc />
         public void SetSystemDecorations(SystemDecorations value)
         {
             var newWindowProperties = _windowProperties;
@@ -783,6 +825,7 @@ namespace Avalonia.Win32
             UpdateWindowProperties(newWindowProperties);
         }
 
+        /// <inheritdoc />
         public void SetTopmost(bool value)
         {
             if (value == _topmost)
@@ -799,6 +842,7 @@ namespace Avalonia.Win32
             _topmost = value;
         }
 
+        /// <inheritdoc />
         public unsafe void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
         {
             if (Win32Platform.WindowsVersion.Build >= 22000)
@@ -829,6 +873,9 @@ namespace Avalonia.Win32
                 IntPtr.Zero);
         }
 
+        [MemberNotNull(nameof(_wndProcDelegate))]
+        [MemberNotNull(nameof(_className))]
+        [MemberNotNull(nameof(Handle))]
         private void CreateWindow()
         {
             // Ensure that the delegate doesn't get garbage collected by storing it as a field.
@@ -845,7 +892,7 @@ namespace Avalonia.Win32
                 style = (int)windowClassStyle,
                 lpfnWndProc = _wndProcDelegate,
                 hInstance = GetModuleHandle(null),
-                hCursor = DefaultCursor,
+                hCursor = s_defaultCursor,
                 hbrBackground = IntPtr.Zero,
                 lpszClassName = _className
             };
@@ -878,20 +925,23 @@ namespace Avalonia.Win32
                     monitor,
                     MONITOR_DPI_TYPE.MDT_EFFECTIVE_DPI,
                     out var dpix,
-                    out var dpiy) == 0)
+                    out _) == 0)
                 {
                     _scaling = dpix / 96.0;
                 }
             }
         }
 
-        private void CreateDropTarget()
+        private void CreateDropTarget(IInputRoot inputRoot)
         {
-            var odt = new OleDropTarget(this, _owner);
+            if (AvaloniaLocator.Current.GetService<IDragDropDevice>() is { } dragDropDevice)
-
-            if (OleContext.Current?.RegisterDragDrop(Handle, odt) ?? false)
             {
-                _dropTarget = odt;
+                var odt = new OleDropTarget(this, inputRoot, dragDropDevice);
+
+                if (OleContext.Current?.RegisterDragDrop(Handle, odt) ?? false)
+                {
+                    _dropTarget = odt;
+                }
             }
         }
 
@@ -1105,7 +1155,7 @@ namespace Avalonia.Win32
 
                 case WindowState.FullScreen:
                     newWindowProperties.IsFullScreen = true;
-                    command = IsWindowVisible(_hwnd) ? (ShowWindowCommand?)null : ShowWindowCommand.Restore;
+                    command = IsWindowVisible(_hwnd) ? null : ShowWindowCommand.Restore;
                     break;
 
                 default:
@@ -1370,13 +1420,13 @@ namespace Avalonia.Win32
         private const int MF_DISABLED = 0x2;
         private const int SC_CLOSE = 0xF060;
 
-        static void DisableCloseButton(IntPtr hwnd)
+        private static void DisableCloseButton(IntPtr hwnd)
         {
             EnableMenuItem(GetSystemMenu(hwnd, false), SC_CLOSE,
                            MF_BYCOMMAND | MF_DISABLED | MF_GRAYED);
         }
 
-        static void EnableCloseButton(IntPtr hwnd)
+        private static void EnableCloseButton(IntPtr hwnd)
         {
             EnableMenuItem(GetSystemMenu(hwnd, false), SC_CLOSE,
                            MF_BYCOMMAND | MF_ENABLED);
@@ -1407,6 +1457,7 @@ namespace Avalonia.Win32
 
         IntPtr EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo.Handle => Handle.Handle;
 
+        /// <inheritdoc />
         public void SetExtendClientAreaToDecorationsHint(bool hint)
         {
             _isClientAreaExtended = hint;
@@ -1414,6 +1465,7 @@ namespace Avalonia.Win32
             ExtendClientArea();
         }
 
+        /// <inheritdoc />
         public void SetExtendClientAreaChromeHints(ExtendClientAreaChromeHints hints)
         {
             _extendChromeHints = hints;
@@ -1433,7 +1485,7 @@ namespace Avalonia.Win32
         public bool IsClientAreaExtendedToDecorations => _isClientAreaExtended;
 
         /// <inheritdoc/>
-        public Action<bool> ExtendClientAreaToDecorationsChanged { get; set; }
+        public Action<bool>? ExtendClientAreaToDecorationsChanged { get; set; }
 
         /// <inheritdoc/>
         public bool NeedsManagedDecorations => _isClientAreaExtended && _extendChromeHints.HasAllFlags(ExtendClientAreaChromeHints.PreferSystemChrome);

src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs

@@ -2,7 +2,6 @@ using System;
 using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
-using Avalonia.Reactive;
 using Avalonia.Controls.Platform;
 using Avalonia.Logging;
 using Avalonia.Threading;
@@ -12,12 +11,12 @@ namespace Avalonia.Win32
     internal class WindowsMountedVolumeInfoListener : IDisposable
     {
         private readonly IDisposable _disposable;
-        private bool _beenDisposed = false;
+        private bool _beenDisposed;
-        private ObservableCollection<MountedVolumeInfo> mountedDrives;
+        private readonly ObservableCollection<MountedVolumeInfo> _mountedDrives;
 
         public WindowsMountedVolumeInfoListener(ObservableCollection<MountedVolumeInfo> mountedDrives)
         {
-            this.mountedDrives = mountedDrives;
+            _mountedDrives = mountedDrives;
 
             _disposable = DispatcherTimer.Run(Poll, TimeSpan.FromSeconds(1));
 
@@ -51,14 +50,14 @@ namespace Avalonia.Win32
                                 })
                                 .ToArray();
 
-            if (mountedDrives.SequenceEqual(mountVolInfos))
+            if (_mountedDrives.SequenceEqual(mountVolInfos))
                 return true;
             else
             {
-                mountedDrives.Clear();
+                _mountedDrives.Clear();
 
                 foreach (var i in mountVolInfos)
-                    mountedDrives.Add(i);
+                    _mountedDrives.Add(i);
                 return true;
             }
         }

src/tools/DevGenerators/Helpers.cs

@@ -6,16 +6,21 @@ namespace Generator;
 
 static class Helpers
 {
+    private static readonly SymbolDisplayFormat s_symbolDisplayFormat =
+        SymbolDisplayFormat.FullyQualifiedFormat.WithMiscellaneousOptions(
+            SymbolDisplayFormat.FullyQualifiedFormat.MiscellaneousOptions |
+            SymbolDisplayMiscellaneousOptions.IncludeNullableReferenceTypeModifier);
+
     public static StringBuilder Pad(this StringBuilder sb, int count) => sb.Append(' ', count * 4);
 
     public static string GetFullyQualifiedName(this ISymbol symbol)
     {
-        return symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
+        return symbol.ToDisplayString(s_symbolDisplayFormat);
     }
     
     public static bool HasFullyQualifiedName(this ISymbol symbol, string name)
     {
-        return symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat) == name;
+        return symbol.ToDisplayString(s_symbolDisplayFormat) == name;
     }
 
     public static bool HasAttributeWithFullyQualifiedName(this ISymbol symbol, string name)
@@ -28,4 +33,4 @@ static class Helpers
 
         return false;
     }
-}
+}