I’m working on a C# application that integrates with a MySQL database to manage and send emails based on certain triggers. The application fetches user information from the database and sends emails if certain conditions are met. However, during the email sending process, I encounter an “Invalid attempt to read when reader is closed” error. This error occurs after handling the connection and reader in a somewhat complex way. Here’s the relevant part of the code:

try
    {
        baglan.Open();
        string projeIdQuery = "SELECT proje_id FROM ferra_orjinal_muadil WHERE ferra_no_b = '" + advancedDataGridView2.Rows[i].Cells["ferra_no_b"].Value.ToString() + "'";
        MySqlCommand projeIdCmd = new MySqlCommand(projeIdQuery, baglan);
        var projeIdResult = projeIdCmd.ExecuteScalar();
        baglan.Close();

        if (projeIdResult != null)
        {
            string projeId = projeIdResult.ToString();
            baglan.Open();
            string emailCheckQuery = "SELECT email_gonderildimi, email, tarih FROM proje_kullanici WHERE proje_id = '" + projeId + "'";
            MySqlCommand emailCheckCmd = new MySqlCommand(emailCheckQuery, baglan);
            using (MySqlDataReader emailCheckReader = emailCheckCmd.ExecuteReader())
            {
                while (emailCheckReader.Read())
                {
                    if (emailCheckReader["email_gonderildimi"].ToString() == "H")
                    {
                        DialogResult dialogResult = MessageBox.Show("Bu filtre için mail gönderilmeyi bekleyen kişiler bulunmakta, mail gönderilsin mi?", "Email Gönderimi", MessageBoxButtons.YesNo);
                        if (dialogResult == DialogResult.Yes)
                        {
                            SmtpClient sc = new SmtpClient
                            {
                                Port = 587,
                                Host = "smtp.ferrafilter.com",
                                Credentials = new System.Net.NetworkCredential("[email protected]", "Bi964Uy1")
                            };
                            MailMessage mail = new MailMessage
                            {
                                From = new MailAddress("[email protected]", "Ferra Filter"),
                                Subject = "Ürün Devreye Alındı",
                                IsBodyHtml = true,
                                Body = "Aşağıda detayı verilmiş olan muadil referanslı ürün, ürün çeşitlerimize eklenmiştir. Kıymetli siparişleri bekliyoruz.<br><br>Aranan Referans: " + advancedDataGridView2.Rows[i].Cells["filtre_no_b"].Value.ToString() + "<br>Tarih: " + emailCheckReader["tarih"].ToString()
                            };
                            mail.To.Add(emailCheckReader["email"].ToString());
                            sc.Send(mail);
                            totalEmailsSent++;

                            baglan.Close();
                            baglan.Open();
                            string updateEmailStatusQuery = "UPDATE proje_kullanici SET email_gonderildimi = 'E', email_gonderim_tarihi = '" + DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "' WHERE proje_id = '" + projeId + "'";
                            MySqlCommand updateEmailStatusCmd = new MySqlCommand(updateEmailStatusQuery, baglan);
                            updateEmailStatusCmd.ExecuteNonQuery();
                            baglan.Close();
                        }
                    }
                }
            }
        }
    }

    catch (Exception ex)
    {
        MessageBox.Show("Bir hata oluştu: " + ex.Message, "Hata", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }

    finally
    {
        if (baglan.State == ConnectionState.Open)
        {
            baglan.Close();
        }
    }

}

if (totalEmailsSent > 0)
{
    MessageBox.Show($"{totalEmailsSent} kişiye başarıyla mail gönderilmiştir.", "Email Gönderildi", MessageBoxButtons.OK, MessageBoxIcon.Information);
}

checkBox5.Checked = false;
cbYeniProjeVerisi.Checked = false;
}