There is no way to check a package's origin.

[Holo-Krzysztof]

The Device Portal Core API reference lists a "PackageOrigin" property under /api/app/packagemanager/packages, but I have not seen it anywhere in the wrapper (more specifically, inside PackageInfo)

The problem is, I'm listing the installed packages so the user can upload to LocalAppData inside her own packages, but it also lists the preinstalled ones from Microsoft, which I cannot open with GetFolderContentsAsync().

[hpsin]

Fixed with #210, thanks @WilliamsJason !