Simple code to expose class for com C# with Example
using System; using System.Runtime.InteropServices; namespace ComLibrary { [ComVisible(true)] public interface IMainType { int GetInt(); void StartTime(); int StopTime(); } [ComVisible(true)] [ClassInterface(ClassInterfaceType.None)] public class MainType : IMainType { private Stopwatch stopWatch; public int GetInt() { return 0; } public void StartTime() { stopWatch= new Stopwatch(); stopWatch.Start(); } public int StopTime() { return (int)stopWatch.ElapsedMilliseconds; } } } (Roslyn)