fix

Author: 0x5bfa

src/Files.App.CsWin32/NativeMethods.txt

@@ -135,3 +135,4 @@ WindowsDeleteString
 IPreviewHandler
 AssocQueryString
 GetModuleHandle
+RegisterClassEx

src/Files.App/ViewModels/UserControls/Previews/ShellPreviewViewModel.cs

@@ -26,7 +26,8 @@ public sealed class ShellPreviewViewModel : BasePreviewModel
 	{
 		PreviewHandler? currentHandler;
 		ContentExternalOutputLink? outputLink;
-		WNDCLASSEXW? wCls;
+		WNDCLASSEXW _windowClass;
+		WNDPROC _windProc = default;
 		HWND hwnd = HWND.Null;
 		bool isOfficePreview = false;
 
@@ -123,10 +124,11 @@ public unsafe void LoadPreview(UIElement presenter)
 
 			fixed (char* pszClassName = szClassName)
 			{
-				var pWindProc = Marshal.GetFunctionPointerForDelegate(WndProc);
+				_windProc = new(WndProc);
+				var pWindProc = Marshal.GetFunctionPointerForDelegate(_windProc);
 				var pfnWndProc = (delegate* unmanaged[Stdcall]<HWND, uint, WPARAM, LPARAM, LRESULT>)pWindProc;
 
-				wCls = new WNDCLASSEXW
+				_windowClass = new WNDCLASSEXW()
 				{
 					cbSize = (uint)Marshal.SizeOf(typeof(WNDCLASSEXW)),
 					lpfnWndProc = pfnWndProc,
@@ -142,6 +144,8 @@ public unsafe void LoadPreview(UIElement presenter)
 					cbWndExtra = 0,
 				};
 
+				PInvoke.RegisterClassEx(_windowClass);
+
 				fixed (char* pszWindowName = szWindowName)
 				{
 					hwnd = PInvoke.CreateWindowEx(
@@ -244,8 +248,7 @@ public void UnloadPreview()
 			//outputLink?.Dispose();
 			outputLink = null;
 
-			if (wCls is not null)
-				PInvoke.UnregisterClass(wCls.Value.lpszClassName, PInvoke.GetModuleHandle(default(PWSTR)));
+			PInvoke.UnregisterClass(_windowClass.lpszClassName, PInvoke.GetModuleHandle(default(PWSTR)));
 		}
 
 		public unsafe void PointerEntered(bool onPreview)