OpenFolderDialog crashing application

https://github.com/AvaloniaUI/Avalonia/blob/9dbcc98a8709d8b185f6f0dc69df19e6873cb97c/src/Windows/Avalonia.Win32/SystemDialogImpl.cs#L112

I keep getting an exception thrown at this location when attempting to execute .ShowAsync() on a FolderOpenDialog. Here is a summary of my code:

private OpenFolderDialog dialog_Source; // Field
{
dialog_Source = new OpenFolderDialog();
dialog_Source.Title = "Select User Folder";
var path = await dialog_Source.ShowAsync(this);
}

Runs fine on Win10 x64, and macOS Big Sur (even in Recovery Mode), but I cannot get this to run in Windows PE. I have run other .NET Core apps fine in this environment, so I know it should be possible. Running this as a self-contained deployment so it should have all the dependencies. Any ideas?

Exception:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Avalonia.Win32.SystemDialogImpl.<>c__DisplayClass2_0.<ShowFolderDialogAsync>b__0() in /_/src/Windows/Avalonia.Win32/SystemDialogImpl.cs:line 112
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
--- End of stack trace from previous location ---
   at UserBackup.MainWindow.click_button_Source(Object sender, RoutedEventArgs e) in ....MainWindow.axaml.cs:line 87

[Splitwirez]

@Splitwirez OK, I was able to get that to build.

Runs in WinPE, and the folder open dialog opens without any issues, but it appears to be a really archaic interface that doesn’t have much functionality.

@imerzan Yeah, I don’t disagree there. That UI is provided by Avalonia itself, and well…I’ve tried to improve it a bit since the 0.10.x releases, but I’m not sure those improvements would be enough for your use case…

Trying to get the updated Win7/10 interface since it allows for click-to-unlock on Bitlocker Locked Drives where it automatically prompts for a Bitlocker Recovery Key. The Managed Dialog doesn’t appear to have it.

…BitLocker whatnow? Yeah I fear that’s…likely beyond my capabilities, unfortunately :C

I’m guessing WinPE is missing a system dependency of some sort for the Avalonia Interface, not sure how I could maybe pack it in with my self-contained app.

Not sure if that’s a thing you can do, nor how, but…best of luck in your search. Hopefully someone else here will have a more…satisfactory answer/solution to offer.

[Splitwirez]

@Splitwirez I can check. Is this implemented within Avalonia or do you mean checking Microsoft.Win32.OpenDileDialog ?

@imerzan It’s a feature within Avalonia - there’s an extension method called UseManagedSystemDialogs() in the Avalonia.Dialogs namespace. Just add that to your AppBuilder.

(You’ll find that in the form of the BuildAvaloniaApp() function in Program.cs, unless you’ve moved it or something)

Side note: Loosely speaking, Microsoft.Win32.FolderBrowserDialog is more or less the opposite of the managed system dialogs.

Also, I should probably clarify: although this may allow you to band-aid your way around the initial problem, I’m not entirely certain whether that initial problem is expected under WinPE or a bug of some sort…