ошибка в windows form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.OleDb;
using System.Data;

namespace biblioteka.Controller
{
    class Query
    {
        OleDbConnection connection;
        OleDbCommand command;
        OleDbDataAdapter dataAdapter;
        DataTable bufferTable;
        public Query(string Conn)
        {
            connection = new OleDbConnection(Conn);
            bufferTable = new DataTable();

        }

        public DataTable UpdatePerson ()
        {
            connection.Open();
            dataAdapter = new OleDbDataAdapter("SELECT * FROM book", connection);
            bufferTable.Clear();
            dataAdapter.Fill(bufferTable);
            connection.Close();
            return bufferTable;
        }

        public void Add(string naimenovanie, int kolichestvo)
        {
            connection.Open();
            command = new OleDbCommand("INSERT INTO book(naimenovanie,kolichestvo) VALUES(@naimenovanie,kolichestvo) ", connection);
            command.Parameters.AddWithValue("naimenovanie",naimenovanie);
            command.Parameters.AddWithValue("kolichestvo",kolichestvo);
            command.ExecuteNonQuery();
            connection.Close();
        }
        public void Delete(int id)
        {
            connection.Open();
            command = new OleDbCommand("DELETE FROM book WHERE id = {id}", connection);
            command.ExecuteNonQuery();
            connection.Close();
        }
    }
}

почему показывает ошибку в public void add на command.ExecuteNonQuery(); при нажатии на insert в windows form