asp.net – SmtpClient.SendAsync调用自动取消

另一方面,同步.发送(…)请求通过就好了.

我的EmailService服务包装器处理从我的ASP.NET MVC 3应用程序中发送带有SmtpClient的异步电子邮件.通过StructureMap将服务实例注入到每个MVC控制器中,它将新的SmtpClient实例包装在using(…){}语句中.

这是我的SmtpClient的EmailService.SendAsync包装器方法：

public void SendAsync(EmailMessage message)
{
    try
    {
        using (var smtpClient = new SmtpClient(_cfg.Host,_cfg.Port)
        {
            EnableSsl = _cfg.EnableSsl,Credentials = _credentials
        })
        {
            smtpClient.SendCompleted += new SendCompletedEventHandler(Email_OnCompleted);

            var mailMessage = new MailMessage(message.From,message.To)
                                {
                                    Subject = message.Subject,Body = message.Body
                                };

            smtpClient.SendAsync(mailMessage,message);

            _logger.Info(string.Format("Sending async email to {0} with subject [{1}]",message.To,message.Subject));
        }
    }
    catch (Exception ex)
    {
        _logger.Error("Async email error: " + ex);
        throw;
    }

}

这是我的Email_OnCompleted委托：

public void Email_OnCompleted(object sender,AsyncCompletedEventArgs e)
{
    var mail = (EmailMessage)e.UserState;

    if (e.Error != null)
    {
        _logger.Error(string.Format("Error sending email to {0} with subject [{1}]: {2}",mail.To,mail.Subject,e.Error));
    }
    else if (e.Cancelled)
    {
        _logger.Warn(string.Format("Cancelled email to {0} with subject [{1}].",mail.Subject));
    }
    else
    {
        _logger.Info(string.Format("Sent email to {0} with subject [{1}].",mail.Subject));
    }
}

为什么异步电子邮件被取消,但同步电子邮件通过正常？这可能是处理问题吗？