EF Core - "A command is already in Progress"

Question

I am requesting a Function in the database where it returns the values to be saved, but before saving I need to make a check if there is no same data, when I do this check with EF core it returns me this error "A command is already in Progress:"

follows code:

       public void funcCompMargemDesvioPadrao()
        {   


            using (var connection = _context.Database.GetDbConnection())
            {

                using (var command = connection.CreateCommand())
                {
                    connection.Open();
                    command.CommandText = "select * from computer_vision.funccompmargemdesviopadrao()";

                    using (var data = command.ExecuteReader())
                    {
                        if (data.HasRows)
                        {
                            while (data.Read())
                            {
                                var objDTO = new Compiled_daily_pass_registerDTO();

                                objDTO.entity_id = Convert.ToInt32(data["id"]);
                                objDTO.pass_date_time = Convert.ToDateTime(data["date_time"]);
                                objDTO.qty_daily_pass = Convert.ToDouble(data["qty_comp"]);
                                objDTO.excluded = false;
                                objDTO.updated_at = DateTime.Now;

                                // AQUI QUE RETORNAR O ERRO
                                compiled_daily_pass_register compiled_day = _context.compiled_daily_pass_register.SingleOrDefault(
                                x => x.pass_date_time == objDTO.pass_date_time && x.entity_id == objDTO.entity_id);

                                objDTO.created_at = compiled_day.created_at;

                                compiled_daily_pass_register obj = new compiled_daily_pass_register();
                                obj = _mapper.Map<Compiled_daily_pass_registerDTO, compiled_daily_pass_register>(objDTO, obj);

                                if (compiled_day != null)
                                {
                                    _context.compiled_daily_pass_register.Remove(compiled_day);
                                    _context.compiled_daily_pass_register.Add(obj);
                                    _context.SaveChanges();
                                }

                            }
                        }
                    }
                }
                connection.Close();

            }