C# 2 adet combobox'da ki saatleri alma

Aşağıda bir örnek bulabilirsin.

Emocan diye bir veri tabanı ve bu veritabanında Rezerve adlı bir tablon olmalı. Bu tabloda Saat(nvarchar(50) türünde bir alana ihtiyacın var.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace emocan
{
    public partial class Form2 : Form
    {
        string baglantiCumlesi = "server=.\\SQLEXPRESS; database=emocan; integrated security=SSPI";
        List<string> RezerveSaatler;
        public Form2()
        {
            InitializeComponent();
            this.comboBox1.DrawMode = DrawMode.OwnerDrawFixed;
            this.comboBox1.DrawItem += new System.Windows.Forms.DrawItemEventHandler(this.comboBox1_DrawItem);
            this.comboBox2.DrawMode = DrawMode.OwnerDrawFixed;
            this.comboBox2.DrawItem += new System.Windows.Forms.DrawItemEventHandler(this.comboBox2_DrawItem);


        }
        private void Form2_Load(object sender, EventArgs e)
        {
            RezerveSaatler = GetirRezerveSaatler();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            var t1 = comboBox1.SelectedItem.ToString();
            var t2 = comboBox2.SelectedItem.ToString();
            bool flag = false;
            foreach (var i in comboBox2.Items)
            {
                if (i.ToString() == t1)
                    flag = true;
                if (flag)
                {
                    if (!DahaOnceRezerveEdilmisMi(i.ToString()))
                        SaatKaydet(i.ToString());
                    else
                    {
                        MessageBox.Show("Bu saat daha önce rezerve edilmiş");
                    }
                }
                if (i.ToString() == t2)
                    flag = false;
            }

        }

        Font myFont = new Font("Arial", 10, FontStyle.Underline | FontStyle.Regular);
        Font myFont2 = new Font("Arial", 10, FontStyle.Italic | FontStyle.Strikeout);

        private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            string saat = comboBox1.Items[e.Index].ToString();
            if (RezerveSaatler.Contains(saat))
            {
                e.Graphics.DrawString(comboBox1.Items[e.Index].ToString(), myFont2, Brushes.LightSlateGray, e.Bounds);


            }
            else
            {
                e.DrawBackground();
                e.Graphics.DrawString(comboBox1.Items[e.Index].ToString(), myFont, Brushes.Black, e.Bounds);
                e.DrawFocusRectangle();
            }


        }
        private void comboBox2_DrawItem(object sender, DrawItemEventArgs e)
        {
            string saat = comboBox2.Items[e.Index].ToString();
            if (RezerveSaatler.Contains(saat))
            {
                e.Graphics.DrawString(comboBox2.Items[e.Index].ToString(), myFont2, Brushes.LightSlateGray, e.Bounds);


            }
            else
            {
                e.DrawBackground();
                e.Graphics.DrawString(comboBox2.Items[e.Index].ToString(), myFont, Brushes.Black, e.Bounds);
                e.DrawFocusRectangle();
            }


        }


        void SaatKaydet(string saat)
        {
            SqlConnection baglanti = new SqlConnection(baglantiCumlesi);
            SqlCommand komut = new SqlCommand("Insert Into Rezerve (Saat) Values (@prmSaat)", baglanti);
            komut.Parameters.AddWithValue("@prmSaat", saat);
            baglanti.Open();
            komut.ExecuteNonQuery();
            baglanti.Close();
        }
        bool DahaOnceRezerveEdilmisMi(string saat)
        {
            SqlConnection baglanti = new SqlConnection(baglantiCumlesi);
            SqlCommand komut = new SqlCommand("Select count(*) from Rezerve Where Saat=@prmSaat", baglanti);
            komut.Parameters.AddWithValue("@prmSaat", saat);
            baglanti.Open();
            int sonuc = (int)komut.ExecuteScalar();
            baglanti.Close();
            if (sonuc == 0)
                return false;
            else
                return true;
        }

        List<string> GetirRezerveSaatler()
        {
            List<string> rezerveler = new List<string>();
            using (SqlConnection connection = new SqlConnection(baglantiCumlesi))
            {
                connection.Open();
                using (SqlCommand command = new SqlCommand("SELECT Saat from Rezerve", connection))
                {
                    SqlDataReader reader = command.ExecuteReader();
                    while (reader.Read())
                    {
                        rezerveler.Add(reader.GetString(0));

                    }
                }
            }
            return rezerveler;
        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox1.SelectedIndex != -1)
            {
                if (RezerveSaatler.Contains(comboBox1.SelectedItem.ToString()))
                    comboBox1.SelectedIndex = -1;
            }


        }

        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (comboBox2.SelectedIndex != -1)
            {
                if (RezerveSaatler.Contains(comboBox2.SelectedItem.ToString()))
                    comboBox2.SelectedIndex = -1;
            }

        }
    }
}