Why isn't my script inheriting from MonoBehaviour

I've opened up my script in visual studio 2015, but I've noticed that none of the classes or variables are appropriately highlighted. I'm not sure whether this is a bug, or more likely something I've done wrong.

The only classes that seem to work are from the System.Collections namespace. The classes in UnityEngine namespace won't even show up in intellisense. I've also made sure the class name is exactly the same as the script name.

Here is an image of visual studio: