How to use scripts from Unity3d project in my separate Visual Studio project?

I have Unity3D project.

I have C# scripts in it.
I have Standard Assets in it.

How to access all that staff, from my separate Visual Studio project?

For example, i cannot use: UnityStandardAssets.Characters.FirstPerson namespace in my project.

Which DLL should i reference, and where is it located?

It is located inside the UnityAssemblies folder in your Library folder which is located in the root of your Unity project.

YourUnityProject\Library\UnityAssemblies\dllName.dll

As for accessing “UnityStandardAssets.Characters.FirstPerson” I don’t think you can unless you reference the scripts inside your project (as standard assets are separate from Unity’s DLL’s).

Lastly I see no reason to be referencing the Unity dll’s in your own project or using the standard assets as they won’t work because they require Unity! It may even be against the Unity EULA to use Unity dll’s and(or) standard assets outside of the Unity Engine.