Hi @kwakminwoo, I assume you are trying to use the Gaze interaction SDK with either the Tobii EyeX or C4 Eye Tracker?
This being the case, you should not necessarily need .NETCORE SDK but a cursory glance on the internet reveals it a product easily installed.
Perhaps if you could kindly be more specific in your intentions and working environment I can provide more assistance.
Have you already installed the Visual Studio? This should take care of any necessary dependencies on your system.