Hello, I've found that in the form of reference you can add a DLL as a project. This is done by a team of dotnet add reference, well or hands it is possible to add.
Actually the question, and as it correctly to use? Studio generally swears and writes that "The referenced component 'interfaces\\Interfaces.csproj' could not be found.", but the error is not fatal and the reference can be referenced without problems and no error occurs. But only if you go and sbility separate plug-in project. But is it possible to make the Studio did a build from the plugin project yourself, when building the main project?