// Compiler options: -target:library using System.Runtime.CompilerServices; using System; [assembly:InternalsVisibleTo("gtest-433")] namespace Blah { // internal by default class Class1 { public void Test() { Console.WriteLine("Class1.Test"); } } // public type with internal member public class Class2 { internal void Test() { Console.WriteLine("Class2.Test"); } internal enum Citrus { Lemon, Lime, Orange } } }