[CommandMethod("ModelSpaceIterator")]

public static void ModelSpaceIterator_Method()

{

    Database database = HostApplicationServices.WorkingDatabase;

    using (Transaction transaction = database.TransactionManager.StartTransaction())

    {

        BlockTableRecord btRecord = (BlockTableRecord)transaction.GetObject(SymbolUtilityServices.GetBlockModelSpaceId(database), OpenMode.ForRead);

        foreach (ObjectId id in btRecord)

        {

            Entity entity = (Entity)transaction.GetObject(id, OpenMode.ForRead);

            //Access to the entity

            MgdAcApplication.DocumentManager.MdiActiveDocument.Editor.WriteMessage(string.Format("\nHandle: {0}", entity.Handle));

        }

        transaction.Commit();

    }

}