GetSelection.cs

[CommandMethod("GetSelection")]
       
        public static void SelectionTest()
        {
            var ed = Application.DocumentManager.MdiActiveDocument.Editor;
            var pso = new PromptSelectionOptions();
            pso.SingleOnly = true;
            pso.SinglePickInSpace = true;
            PromptSelectionResult psr;
            var ids = new ObjectIdCollection();
            while (true)
            {
                psr = ed.GetSelection(pso);
                if (psr.Status != PromptStatus.OK)
                    break;
                ids.Add(psr.Value[0].ObjectId);
                ed.WriteMessage("\n{0} selected objects", ids.Count);
            }
        }