如果电子邮件失败,我使用这个相当标准的代码：

static void CheckExceptionAndResend(SmtpFailedRecipientsException ex,SmtpClient client,MailMessage message)
    {
        for (int i = 0; i < ex.InnerExceptions.Length -1; i++)
        {
            var status = ex.InnerExceptions[i].StatusCode;

            if (status == SmtpStatusCode.MailBoxBusy ||
                status == SmtpStatusCode.MailBoxUnavailable ||
                status == SmtpStatusCode.TransactionFailed)
            {
                System.Threading.Thread.Sleep(3000);
                client.Send(message);
            }
        }
    }

但是,我正在尝试使用SendAsync()实现相同的目标.这是我到目前为止的代码：

public static void SendAsync(this MailMessage message)
    {
        message.ThrowNull("message");

        var client = new SmtpClient();

        // Set the methods that is called once the event ends
        client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);

        // Unique identifier for this send operation
        string userState = Guid.NewGuid().ToString();

        client.SendAsync(message,userState);

        // Clean up
        message.dispose();
    }

    static void SendCompletedCallback(object sender,AsyncCompletedEventArgs e)
    {
        // Get the unique identifier for this operation.
        String token = (string)e.UserState;

        if (e.Error.IsNotNull())
        {
            // Do somtheing
        }
    }

问题是使用令牌和/或e.Error如何获取异常,以便我可以对StatusCode进行必要的检查然后重新发送？

我整个下午一直在谷歌搜索,但没有找到任何积极的东西.

任何建议表示赞赏

更新：

检查Exception是否为SmtpException类型,如果是,则可以查询StatusCode.就像是

if(e.Exception is SmtpException)
{
   SmtpStatusCode  code = ((SmtpException)(e.Exception)).StatusCode;
   //and go from here...
}

和check here了解更多细节.

当我发送消息没有附件它工作正常。
当我发送包含至少一个内存中附件的消息时，它会失败。

所以，我想知道是否可以使用异步方法与内存中的附件。

这里是发送方法

public static void Send() {

        MailMessage message = new MailMessage("from@foo.com","too@foo.com");
        using (MemoryStream stream = new MemoryStream(new byte[64000])) {
            Attachment attachment = new Attachment(stream,"my attachment");
            message.Attachments.Add(attachment);
            message.Body = "This is an async test.";

            SmtpClient smtp = new SmtpClient("localhost");
            smtp.Credentials = new NetworkCredential("foo","bar");
            smtp.SendAsync(message,null);
        }
    }

这是我当前的错误

System.Net.Mail.SmtpException: Failure sending mail.
 ---> System.NotSupportedException: Stream does not support reading.
   at System.Net.Mime.MimeBasePart.EndSend(IAsyncResult asyncResult)
   at System.Net.Mail.Message.EndSend(IAsyncResult asyncResult)
   at System.Net.Mail.SmtpClient.SendMessageCallback(IAsyncResult result)
   --- End of inner exception stack trace ---

解

public static void Send()
    {

            MailMessage message = new MailMessage("from@foo.com","to@foo.com");
            MemoryStream stream = new MemoryStream(new byte[64000]);
            Attachment attachment = new Attachment(stream,"my attachment");
            message.Attachments.Add(attachment);
            message.Body = "This is an async test.";
            SmtpClient smtp = new SmtpClient("localhost");
            //smtp.Credentials = new NetworkCredential("login","password");

            smtp.SendCompleted += delegate(object sender,System.ComponentModel.AsyncCompletedEventArgs e)
            {
                    if (e.Error != null)
                    {
                            System.Diagnostics.Trace.TraceError(e.Error.ToString());

                    }
                    MailMessage userMessage = e.UserState as MailMessage;
                    if (userMessage != null)
                    {
                            userMessage.dispose();
                    }
            };

            smtp.SendAsync(message,message);
    }