如何发送邮件异步？

Question

namespace Binarios.admin
{
    public class SendEmailGeral
    {
        public SmtpClient client = new SmtpClient("smtp.gmail.com", 587);
        public MailMessage msg = new MailMessage();

        public void Enviar(string sendFrom, string sendTo, string subject, string body)
        {    
            string pass = "12345";
            System.Net.NetworkCredential smtpCreds = new System.Net.NetworkCredential(sendFrom, pass);

            //setup SMTP Host Here
            client.UseDefaultCredentials = false;
            client.Credentials = smtpCreds;
            client.EnableSsl = true;

            MailAddress to = new MailAddress(sendTo);
            MailAddress from = new MailAddress(sendFrom);

            msg.IsBodyHtml = true;
            msg.Subject = subject;
            msg.Body = body;
            msg.From = from;
            msg.To.Add(to);

            client.Send(msg);
        }
    }
}

我有这个代码,但我想改进它,我可以发送邮件异步.您能否提出改进这段代码或其他方法的建议.我尝试过visual studio建议但不能使用它们的异步属性.

Answer 1

SmtpClient允许您异步发送,并使用事件在发送完成时通知您.这可能不适合使用,因此您可以创建一个扩展方法来返回Task:

public static Task SendAsync(this SmtpClient client, MailMessage message)
{
    TaskCompletionSource<object> tcs = new TaskCompletionSource<object>();
    Guid sendGuid = Guid.NewGuid();

    SendCompletedEventHandler handler = null;
    handler = (o, ea) =>
    {
        if (ea.UserState is Guid && ((Guid)ea.UserState) == sendGuid)
        {
            client.SendCompleted -= handler;
            if (ea.Cancelled)
            {
                tcs.SetCanceled();
            }
            else if (ea.Error != null)
            {
                tcs.SetException(ea.Error);
            }
            else
            {
                tcs.SetResult(null);
            }
        }
    };

    client.SendCompleted += handler;
    client.SendAsync(message, sendGuid);
    return tcs.Task;
}

要获得发送任务的结果,您可以使用ContinueWith:

Task sendTask = client.SendAsync(message);
sendTask.ContinueWith(task => {
    if(task.IsFaulted) {
        Exception ex = task.InnerExceptions.First();
        //handle error
    }
    else if(task.IsCanceled) {
        //handle cancellation
    }
    else {
        //task completed successfully
    }
});