Code working in Eclipse doesn't run in Visual Studio

I'm trying to move to Visual Studio from development in Eclipse previously.

Visual Studio and Monkey C plugin installed properly, verified in VS.

No code that worked in Eclipse will run in the VS environment. To make sure it wasn't due to my rusty coding skills,

I downloaded and tried to run the Crystal watch face, after downloading its code from github.

It doesn't run either, giving me a bunch of errors.

What am I doing wrong? Is there an error checking level that is higher in VS than Eclipse?

Help!