Here is code:

using SolidWorks.Interop.sldworks;
using SolidWorks.Interop.swconst;
using System.Diagnostics; 
using System;

namespace STEPExporter.csproj
{
   public partial class SolidWorksMacro
   {
       public void Main()
       {
           Debug.WriteLine("Starting..");

           int swAPIWarnings = 0;
           int swAPIErrors = 0;

           IModelDoc2 swActiveDoc = swApp.ActiveDoc as IModelDoc2;
           IAssemblyDoc swAssembly = swActiveDoc as IAssemblyDoc;

Object