public IFileSystem ChooseFileSystem(string lastFileSystemId)
{
var fs = FileSystems.FirstOrDefault(x => x.IsAvailable && x.Id == lastFileSystemId);
#if __IOS__
if (fs == null)
{
fs = FileSystems.OfType <DeviceFileSystem> ().First(x => x.IsAvailable);
}
#endif
if (fs == null)
{
fs = FileSystems.First(x => x.IsAvailable);
}
return(fs);
}