I think I understand. If you want to work with the Pega Robotics strictly through C# - you would need to create a C# Project and utilize a dll generated from a Pega Robotics Project. You would, at minimum, create adapters in a Pega Robotics Project and interrogate controls that would be later automated. Then in your C# Project, you can design your automations in code.
Based on the screenshot... I see "New Project" in Visual Studio 2015 and there are options to Create a Pega Robotics Project or an Empty Pega Robotics Project. That means that you have Pega Robotics installed already. There is no C# Project in Pega Robotics. Visual C# is the only C# project that you can create.