Asp.Net Identity 2.0 - How to Implement IIdentityMessageService to do Async SMTP using SmtpClient?

Question

I've implemented a simple EmailService for Asp.Net Identity 2.0 (via the IIdentityMessageService interface.

    public class EmailService : IIdentityMessageService
{
    public Task SendAsync(IdentityMessage message)
    {
        // convert IdentityMessage to a MailMessage
        var email = 
           new MailMessage(new MailAddress("noreply@mydomain.com", "(do not reply)"), 
           new MailAddress(message.Destination))
        {
            Subject = message.Subject,
            Body = message.Body,
            IsBodyHtml = true
        };

        using (var client = new SmtpClient()) // SmtpClient configuration comes from config file
        {
            return client.SendMailAsync(email);
        }
    }
}

To send an email, I go through UserManager:

await _userManager.SendEmailAsync(user.Id, "Confirm your account","Please confirm your account by clicking this link: <a href=\"" + callbackUrl + "\">link</a>");

The problem is that I get a System.Threading.Tasks.TaskCanceledException when I call SendEmailAsync() and it's not clear why.

If I send email synchronously (client.Send(email)), everything works fine.

So my questions are:

How do I prevent the TaskCanceledException from getting thrown? and (assuming I can overcome this error),
How should I go about communicating errors during email sending back to the client (i.e., "no such user here" type responses from the SmtpClient?

Here is your details answer https://stackoverflow.com/a/45789677/3835843 — Arif, Aug 21 '17 at 05:37

meziantou · Accepted Answer · 2014-04-02T14:34:45.557

31

Your problem is that SmtpClient is disposed before the email is sent.

Two ways:

Await the SendMailAsync result

using (var client = new SmtpClient())
{
    await client.SendMailAsync(email);
}

Register the SendCompleted event and dispose the SmtpClient only after the message is sent

var client = new SmtpClient();
client.SendCompleted += (s, e) => {
    client.Dispose();
};
return client.SendMailAsync(message);

edited Apr 02 '14 at 14:34

answered Apr 01 '14 at 22:13

meziantou

20,589
7
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83

I can't await the SendMailAsync() (at least not with out some more gymnastics) because the IIdentityMessageService.SendAsync() method has a return type of Task. But the second suggestion looks like it's going to work. Thanks. – Mr. T Apr 02 '14 at 14:15
7

You can await the `SendMailAsync` method. Add `async`/`await` and do not return anything. The compiler will do his job. – meziantou Apr 02 '14 at 14:27
4

I faced this same issue and wrote up a complete description here: http://blog.falafel.com/avoid-taskcanceledexception-sending-email-async/ – ssmith Sep 25 '14 at 13:34
what if I make `client` static? – Wolfrevok Cats Oct 15 '18 at 17:53
In this case, you need to make sure all `SendMailAsync` has completed before disposing the client. You can ask a new question with your code, so we can help you. – meziantou Oct 15 '18 at 18:36
My realization is very simple. It works without any errors (noticeable, at least): `public class EmailService : IIdentityMessageService { static SmtpClient Sender =new SmtpClient(); public Task SendAsync(IdentityMessage m) { return Task.Factory.StartNew(()=>{ Sender.Send(new MailMessage("robot@service.com", m.Destination,m.Subject,""+m.Body+""){IsBodyHtml=true}); }); } }` But I now I'm in doubt if it is really correct. Especially with that approach to `async` method. – Wolfrevok Cats Oct 19 '18 at 21:16

score 9 · Answer 2 · answered Oct 27 '16 at 13:49

You must put async on method.

    public async Task SendAsync(IdentityMessage message)
    {
        using (SmtpClient client = new SmtpClient())
        {
                using (var mailMessage = new MailMessage("your@email.com", message.Destination, message.Subject, message.Body))
                {
                    await client.SendMailAsync(mailMessage);
                }
            }
        }
    }

Asp.Net Identity 2.0 - How to Implement IIdentityMessageService to do Async SMTP using SmtpClient?

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