Can't add script behaviour VisualContainerAsset. The script needs to derive from MonoBehaviour!

First picture im dragging c# file to player folder.

 

Well, the error just says a script you're trying to add doesn't inherit from Monobehaviour, so you can't add it directly as a component to a gameobject.

If it does inherit from monobehaviour and you are getting this error, restart Unity. I think we had that happen here at work once and restarting fixed it.