PCLExt.FileStorage is a bait-and-switch library that was designed to implement a storage API in portable(PCL) projects.
It was formely a basic fork of PCL Storage, but later formed it's own set of API's designed to ease use of files and folders in managed code. It has a more "OOP" approach.

PCLExt.FileStorage supports .NET Framework (4.5), .NET Standard (2.0), Xamarin.iOS, Xamarin.Android, Xamarin.Mac and UWP. This makes it easier to create cross-platform .NET libraries and apps.

Examples and API documentation can be found here.