How can I add a reference to the library which is not C# Script from Visual Studio?

I’m trying to add a reference to the library which is not C# script (Pointgrey, Spinnaker)

In an ordinary C# project, I can add the reference to the .dll file from Visual Studio.
(Reference → Add reference, and I can use the library)

From the Visual Studio, however, which is activated from Unity (Edti Script), I cannot add a reference like an ordinary C# project.

How can I add a reference to the .dll file in Visual Studio editting the Unity scripts

My environment is as follows,
Unity 5.6.1
Visual Studio 2017

Best regards,

You can’t, not directly. Unity needs to know about your DLL in order to build your game so you need to do it the way Unity allows.

If you put the DLL under your Assets folder Unity will find it and if you ask nicely, you may even get to call it from your C# code. But it better be .Net 3.5 or native code if you want to run it in the editor. See Plugins in the docs.

Step to glory:

Create a folder in assest called Plugins: unity use this folder to load your external DLLs, if you put here unity install the DLLs automatic, and you just need to add Using yourDLL in your project and it works. If the error “The type or namespace name ‘Data’ does not exist in the namespace ‘System’, are you missing ‘System.data’ assembly reference?” happens just try to download another version (if you tried 32 bits dll try a 64 bits dll)