Implement WellKnownFolder.ApplicationData

[maxkatz6]

Is your feature request related to a problem? Please describe.

This one isn't related nor useful for the file picker purposes, but is useful if developers want to have a reusable API to write application state where there always will be read and write access.

Implementation details:

• Windows (packaged) - use ApplicationData.LocalFolder from WinRT API.
  Windows (unpackaged) - create application subfolder in LocalAppData folder (maybe, WinAppSDK has something now to use here).
• macOS - ~/Library/Application Support/ApplicationName
• linux - /var/lib/myapp supposedly (and environment variables that can redefine this)
• Browser - StorageManager.getDirectory() (unexpectedly, even gets support on Mozilla).
• iOS - see macOS
• Android - Context.getFilesDir()

some of these platforms can be handled by standard Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) (which can be used even now). But not on all platforms.
For unpackaged windows, linux and macos it possibly should be configurable, as we would need to create an application folder with application name.

[aleh4d]

WellKnownFolder.ApplicationData is needed any way.
I want to use LiteDB as a storage for the app, but it is impossible in Avalonia,
For some reason that is easy in MAUI, as it has the means for cross-platform storage reference.
All it needs is AppDataDirectory, AppCacheDirectory and OpenAppPackageFile, which Avalinia misses,
and Avalonia.Essentials project is abandoned (and merged to MAUI space) and incomplete, and does not work for desktop.
And Xamarin.Essentials also does not compile for Avalonia.Desktop.
So Avalonia is severely incomplete here, and I deem to be forced to switch to MAUI for development.

[timunie]

@aleh4d a contribution is welcome. Or you can ask for paid support if you need this feature urgently. Other than that it's planned but we have no due date yet.

We hope you will stay with us but if MAUI suits your particular needs better, we don't blame you.

[maxkatz6]

but it is impossible in Avalonia

It is very well possible in many different ways.
I even mentioned in the first comment, you can use Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) which should work everywhere except Browser. But LiteDB doesn’t make sense there anyway, as you should use IndexedDB APIs instead.

Or you can call native apis by youself, but .NET BCL api did it already.

[MarkFajfar]

Just to add, it would be helpful for the documentation to mention the use of Environment.GetFolderPath...
I needed to save application state for an Android app, and it took a few hours of searching the internet to find this.
The documents explain how to use ReactiveUI for data persistence, but for me that is overkill just to write a short text file (and I'm not otherwise using Reactive).
So the documentation should say whether Environment.GetFolderPath... is a correct way to save state, or is there some other method.
(FYI the resource that helped me: https://learn.microsoft.com/en-us/previous-versions/xamarin/android/platform/files/ )

[katatunix]

I tried Environment.GetFolderPath(Environment.SpecialFolder.* and it works well on Debug mode but crashes on Release mode. I will post a minimal sample later but it's basically from Avalonia.Templates and change the greeting message to Environment.GetFolderPath(Environment.SpecialFolder.*.

[katatunix]

I tried Environment.GetFolderPath(Environment.SpecialFolder.* and it works well on Debug mode but crashes on Release mode. I will post a minimal sample later but it's basically from Avalonia.Templates and change the greeting message to Environment.GetFolderPath(Environment.SpecialFolder.*.

Nevermind, I delete the bin and obj folders then rebuild, now it works.