c# - 在 ASP.NET C# 中异步发送电子邮件

Question

我想知道是否有一种方法可以在 asp.net c# 中异步发送电子邮件。我使用以下代码发送电子邮件:

 if (checkObavijest.Checked)
            {
                List<hsp_Kupci_Newsletter_Result> lista = ServisnaKlasa.KupciNewsletter();
                for (int i = 0; i < lista.Count; i++)
                {
                    MailMessage mail = new MailMessage();

                    mail.From = new MailAddress("*******");
                    mail.To.Add(lista[i].Email);
                    mail.Subject = "Subject";
                    mail.SubjectEncoding = Encoding.UTF8;
                    mail.BodyEncoding = Encoding.UTF8;
                    mail.IsBodyHtml = true;
                    mail.Priority = MailPriority.High;
                    mail.Body = "Some message";
                    SmtpClient smtpClient = new SmtpClient();
                    Object state = mail;
                    smtpClient.Credentials = new NetworkCredential("****@gmail.com", "****");
                    smtpClient.Port = 587;
                    smtpClient.Host = "smtp.gmail.com";
                    smtpClient.EnableSsl = true;
                    smtpClient.SendCompleted += new SendCompletedEventHandler(smtpClient_SendCompleted);
                    try
                    {
                        smtpClient.SendAsync(mail, state);
                    }
                    catch (Exception ex)
                    {

                    }
                }

 void smtpClient_SendCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
        {

            MailMessage mail = e.UserState as MailMessage;

            if (!e.Cancelled && e.Error != null)
            {
                string poruka = "Emailovi poslani!";
                ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('" + poruka + "');", true);
            }
        }

但是当我勾选发送电子邮件的选项时，页面加载大约 40 秒，然后在 40 秒后发送电子邮件。如您所见，我目前从我的数据库中提取了 20-30 封电子邮件。我认为这是异步发送邮件的正确方法，但显然不是... 我怎样才能将电子邮件发送到另一个线程，这样它就不会影响正在使用此页面的用户？有人可以帮我解决这个问题吗？谢谢!

Answer 1

原因在 MSDN documentation on SmtpClient.SendAsync 上提到

After calling SendAsync, you must wait for the e-mail transmission to complete before attempting to send another e-mail message using Send or SendAsync.

您可以通过包装方法调用使用 ThreadPool 调用 SendAsync。这会给你一些类似即发即弃的场景。

像这样:

public void SendViaThread(System.Net.Mail.MailMessage message) {
    try {
        System.Threading.ThreadPool.QueueUserWorkItem(SendViaAsync, message);
    } catch (Exception ex) {
        throw;
    }
}

private void SendViaAsync(object stateObject) {
    System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient();
    System.Net.Mail.MmailMessage message = (MmailMessage)stateObject;
    ...
    smtp.Credentials = new NetworkCredential("...");
    smtp.Port = 587;
    smtp.Host = "...";
    ...
    smtp.SendCompleted += new SendCompletedEventHandler(smtpClient_SendCompleted);
    ...
    smtp.Send(message);
}

然后您将在代码中调用 SendViaThread(mail)。所以，你的循环现在变成了:

for (int i = 0; i < lista.Count; i++) {
    MailMessage mail = new MailMessage();
    mail.From = new MailAddress("...");
    mail.To.Add(lista[i].Email);
    mail.Subject = "...";
    ...
    mail.Body = "...";
    SendViaThread(mail);
 }