Saving the progress of a Unity game in isolated storage

Hi,

I am building a Unity game targetted for Windows Store 8.1 and I need to save game progress in isolated storage. But using 'await' operator in accessing the local storage gives me this error

 'await' requires that the type 'Windows.Foundation.IAsyncOperation<Windows.Storage.StorageFile>' have a suitable GetAwaiter method. Are you missing a using directive for 'System'?

Is there a way i can use 'await' operator somehow?

I figured if I implement my Save method in the solution generated after exporting the project to Windows 8.1 it would work fine. Trouble is I am not sure how to access the variables and methods(required in saving the game) of the unity script in the main solution.

Can anyone help with any of these approaches or if there is a better one?