Why there are sooo many .cu files excluded from build in most SDK examples?

Hi everybody, I’m trying to implement a stochastic optimization solver for my large scale machine learning project. I never use CUDA before so I have to start from scratch. When I’m reading those examples provided by Parallel Computing SDK (notably the ‘cppIntegration’) I notice that a lot of .cu files that contains kernel processes are excluded from build (there is a red ‘-’ displayed on its file icon), and its properties box shows ‘custom build tool’ without any parameter, when I’m trying to include it into the building process and change the build tool/library to default toolset for .cu files/cutil application the visual studio gave me a bunch of linking error. It seems like cuda builder can’t even go through its own examples.

Projects that doesn’t contains an independent kernel process .cu file won’t have such problem, and can go through the entire toolset. Did anybody encounter this situation before?