ExecuteReader: Connection Property has not been initialized

I have ExecuteReader error. I have tried to connect database and get some values from my database. I have searched but can not figure it out. Here is my code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.OleDb;
using System.Data;
using System.Windows;
using System.Drawing;
using System.Collections;
using Microsoft.VisualBasic;
using System.IO;
using System.Windows.Forms;

namespace PhoneCaseWFA
{
    class Database
    {
        private OleDbConnection bag = new OleDbConnection();
        private OleDbCommand komut = new OleDbCommand();
        private OleDbDataReader reader = null;
        public DataTable datatable = new DataTable();
        string Ad, Soyad, EPosta, DogumTar;
    int TelefonNum, PinKodu, Kimlik, KasaNum;

    public void TabloBaglantisi()
    {
        string baglanti = "Provider = Microsoft.ACE.OLEDB.12.0; Source = SarjVeritabani.mdb; Persist Security Info = False;";
        bag.Close();
        bag.ConnectionString = baglanti;

        try
        {
            bag.Open();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

        OleDbDataAdapter adapter = new OleDbDataAdapter("Select * From SarjVerileri", baglanti);
        adapter.Fill(datatable);
    }

    public Database()
    {
        string baglanti = "Provider = Microsoft.ACE.OLEDB.12.0; Data Source = SarjVeritabani.mdb; Persist Security Info = False;";
        bag.ConnectionString = baglanti;

        try
        {
            bag.Open();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
    }

    public int KasaNoBul()
    {
        string Kasalar = "SELECT KasaNumarasi FROM KasaKontrol";

        int kasa1 = 10000000, kasa2 = 01000000, kasa3 = 00100000, kasa4 = 00010000,
            kasa5 = 00001000, kasa6 = 00000100, kasa7 = 00000010, i = 0, j = 0,
            boskasa = 00000000;

        int[] KasaNo = new int[7];

        if (bag.State == ConnectionState.Closed)
            bag.Open(); //It gives me error here

        komut.Connection = bag;
        komut.CommandText = Kasalar;
        reader = komut.ExecuteReader();

        while (reader.Read())
        {
            KasaNo[i] = Convert.ToInt32(reader);
            i++;
        }

        reader.Close();

        while(j<7)
        {
            if (kasa1 != KasaNo[j])
            {
                boskasa = kasa1;
                break;
            }

            else if (kasa2 != KasaNo[j])
            {
                boskasa = kasa2;
                break;
            }

            else if (kasa3 != KasaNo[j])
            {
                boskasa = kasa3;
                break;
            }

            else if (kasa4 != KasaNo[j])
            {
                boskasa = kasa4;
                break;
            }

            else if (kasa5 != KasaNo[j])
            {
                boskasa = kasa5;
                break;
            }

            else if (kasa6 != KasaNo[j])
            {
                boskasa = kasa6;
                break;
            }

            else if (kasa7 != KasaNo[j])
            {
                boskasa = kasa7;
                break;
            }

            j++;
        }

        return boskasa;
    }

This is some of my code. I donnot know how to figure it out. If anybody can help me I'll be greatfull.