asp.net – 有没有办法使用System.Net.Mail.SendAsync()捕获异常

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.

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