Skip the path: stick to the StorageFile：
Converting a StorageFile to a path to remember it for later is often workable, but you will need to have a fallback identifier for path-less StorageItems. The Windows.Storage.AccessCache namespace provides classes to remember StorageItems so they can be reloaded later without requiring the user to go through the picker. The StorageApplicationPermissions.FutureAccessList provides random access to items that have been previously used. The MostRecentlyUsedList allows keeping a list of recently used locations. See How to track recently used files and folders and the File picker sample and the File access sample).