Intermittent Problem with Preferences on Windows

[david-maw]

Description

I get an intermittent IOException failure ("The process cannot access the file '...\Settings\preferences.dat' because it is being used by another process") trying to set a preference while exiting a MAUI program, probably as a result of a Window.Deactivated event. I have not been able to reproduce it in a simple test case, but it happens from time to time in my complex (about 16k lines of C# and XAML) app. I've added a link to the app repository below in case you want to look at the code.

Here's what the failure looks like, if you want me to collect more or different information next time it happens, I can.

System.IO.IOException
  HResult=0x80070020
  Message=The process cannot access the file 'C:\Users\david\AppData\Roaming\Microsoft\D9049CD2-5037-432D-BC7E-2E2FB39EBA1C\Settings\preferences.dat' because it is being used by another process.
  Source=System.Private.CoreLib
  StackTrace:
   at Microsoft.Win32.SafeHandles.SafeFileHandle.CreateFile(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options)
   at Microsoft.Win32.SafeHandles.SafeFileHandle.Open(String fullPath, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.Strategies.OSFileStreamStrategy..ctor(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.Strategies.FileStreamHelpers.ChooseStrategyCore(String path, FileMode mode, FileAccess access, FileShare share, FileOptions options, Int64 preallocationSize, Nullable`1 unixCreateMode)
   at System.IO.File.Create(String path)
   at Microsoft.Maui.Storage.UnpackagedPreferencesImplementation.Save()
   at Microsoft.Maui.Storage.UnpackagedPreferencesImplementation.Set[T](String key, T value, String sharedName)
   at Microsoft.Maui.Storage.PreferencesImplementation.Set[T](String key, T value, String sharedName)
   at Microsoft.Maui.Storage.Preferences.Set(String key, Boolean value, String sharedName)
   at Microsoft.Maui.Storage.Preferences.Set(String key, Boolean value)
   at DivisiBill.Services.AppSettings.set_MealSavedToFile(Boolean value) in H:\Develop\Phone\DivisiBill\DivisiBill\Services\AppSettings.cs:line 77
   at DivisiBill.Models.Meal.SaveToFile() in H:\Develop\Phone\DivisiBill\DivisiBill\Models\Meal.cs:line 1211
   at DivisiBill.Models.Meal.<SaveToFileAsync>b__89_0() in H:\Develop\Phone\DivisiBill\DivisiBill\Models\Meal.cs:line 1178
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)

Steps to Reproduce

Itt's not reproducible to order.

Link to public reproduction project repository

https://github.com/david-maw/DivisiBill.git

Version with bug

9.0.21 SR2.1

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

8.0.93 SR9.3

Affected platforms

Windows

Affected platform versions

Windows 11

Did you find any workaround?

No

Relevant log output