Mr. T Mr. T - 1 month ago 17
C# Question

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

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?


Answer

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);