UnityWebRequest does not exist within UnityEngine.Networking

I'm writing a c# class library that uses some UnityEngine.dll features.

However I can't seem to access UnityEngine.Networking.UnityWebRequest

Has this been set to internal? I'm able to use plenty of other functions with UnityEngine.dll. And i've also been able to access this class within unity itself. Is there something i'm missing that is needed to access this feature?

Or does anyone know any workarounds? (The namespace does seem to exist within UnityEngine.Experimental.Networking, but it produces warnings about being deprecated and doesn't seem to run within a co-routine. The UnityWebRequest.Get method also doesn't seem to exist once you import it into unity).

Thanks,

Sam