If you want to use an Ethernet address(like 192.168.0.1) to send http request, you may meet the error：
A network capability is required to access this network resource.
So the solution here:
Package.appxmanifest -> Capabilities tab -> Check Private Networks (Client & Server) capability.
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
Because your csproj configuration may not correct configured.
Open the csproj file(project file) with text, make sure
<UseDotNetNativeToolchain>false</UseDotNetNativeToolchain>is TRUE, that's it.