UWP Folders overview

Library Folders:
KnownFolders.AppCaptures
KnownFolders.CameraRoll
KnownFolders.DocumentsLibrary
KnownFolders.HomeGroup
KnownFolders.MediaServerDevices
KnownFolders.MusicLibrary
KnownFolders.Objects3D
KnownFolders.Playlists
KnownFolders.RecordedCalls
KnownFolders.RemovableDevices
KnownFolders.SavedPictures
KnownFolders.VideosLibrary

Local Data Folder:
ApplicationData.Current.LocalFolder

Installation Folder:
Windows.ApplicationModel.Package.Current.InstalledLocation

Could not create Appxupload under AppPackages folder in UWP

Because your csproj configuration may not correct configured.

Open the csproj file(project file) with text, make sure

is TRUE, that’s it.