PickObjectLayer.cs

 [CommandMethod("SelectionFilter")]
         
        public static  void LayerSelection()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;
            TypedValue[] filterlist = new TypedValue[2];
            //select circle and line
            filterlist[0] = new TypedValue(0, "CIRCLE,LINE");
            //8 = DxfCode.LayerName
            filterlist[1] = new TypedValue(8, "0,Layer1,Layer2");
            SelectionFilter filter =
                new SelectionFilter(filterlist);
            PromptSelectionResult selRes = ed.SelectAll(filter);
            if (selRes.Status != PromptStatus.OK)
            {
                ed.WriteMessage(
                    "\nerror in getting the selectAll");
                return;
            }
            ObjectId[] ids = selRes.Value.GetObjectIds();

            ed.WriteMessage("No entity found: "

                            + ids.Length.ToString() + "\n");
        }