How to send asynchronous letters?

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);
        }
    }
}

I have this code, but I would like to improve it so that I can send asynchronous letters. Could you suggest any idea to improve this part of the code or another way to do it. I tried the asynchronous properties that the visual studio offered, but could not use them.

Answer 1

SmtpClientAllows sending asynchronously and uses events to notify completion of sending. This can be hard to use, so you can create an extension method to return 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;
}

To get the result of a submit task, you can use 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
    }
});

Answer 2

, SendAsync !

Answer 3

Change your code:

 client.Send(msg);

To:

client.SendAsync(msg);

more details

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