Asynchronously sending Emails in C#?

Question

I'm developing an application where a user clicks/presses enter on a certain button in a window, the application does some checks and determines whether to send out a couple of emails or not, then show another window with a message.

My issue is, sending out the 2 emails slows the process noticeably, and for some (~8) seconds the first window looks frozen while it's doing the sending.

Is there any way I can have these emails sent on the background and display the next window right away?

Please don't limit your answer with "use X class" or "just use X method" as I am not all too familiarized with the language yet and some more information would be highly appreciated.

Thanks.

Answer 1

Here is a fire and forget approach together with async using .Net 4.5.2+:

BackgroundTaskRunner.FireAndForgetTaskAsync(async () =>
{
    SmtpClient smtpClient = new SmtpClient(); // using configuration file settings
    MailMessage message = new MailMessage(); // TODO: Initialize appropriately
    await smtpClient.SendMailAsync(message);
});

where BackgroundTaskRunner is:

public static class BackgroundTaskRunner
{     
    public static void FireAndForgetTask(Action action)
    {
        HostingEnvironment.QueueBackgroundWorkItem(cancellationToken => // .Net 4.5.2+ required
        {
            try
            {
                action();
            }
            catch (Exception e)
            {
                // TODO: handle exception
            }
        });
    }

    /// <summary>
    /// Using async
    /// </summary>
    public static void FireAndForgetTaskAsync(Func<Task> action)
    {
        HostingEnvironment.QueueBackgroundWorkItem(async cancellationToken => // .Net 4.5.2+ required
        {
            try
            {
                await action();
            }
            catch (Exception e)
            {
                // TODO: handle exception
            }
        });
    }
}

Works like a charm on Azure App Services.

Answer 2

As it's a small unit of work you should use ThreadPool.QueueUserWorkItem for the threading aspect of it. If you use the SmtpClient class to send your mail you could handle the SendCompleted event to give feedback to the user.

ThreadPool.QueueUserWorkItem(t =>
{
    SmtpClient client = new SmtpClient("MyMailServer");
    MailAddress from = new MailAddress("[e-mail]", "My Name", System.Text.Encoding.UTF8);
    MailAddress to = new MailAddress("[e-mail]");
    MailMessage message = new MailMessage(from, to);
    message.Body = "The message I want to send.";
    message.BodyEncoding =  System.Text.Encoding.UTF8;
    message.Subject = "The subject of the email";
    message.SubjectEncoding = System.Text.Encoding.UTF8;
    // Set the method that is called back when the send operation ends.
    client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);
    // The userState can be any object that allows your callback 
    // method to identify this send operation.
    // For this example, I am passing the message itself
    client.SendAsync(message, message);
});

private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
{
        // Get the message we sent
        MailMessage msg = (MailMessage)e.UserState;

        if (e.Cancelled)
        {
            // prompt user with "send cancelled" message 
        }
        if (e.Error != null)
        {
            // prompt user with error message 
        }
        else
        {
            // prompt user with message sent!
            // as we have the message object we can also display who the message
            // was sent to etc 
        }

        // finally dispose of the message
        if (msg != null)
            msg.Dispose();
}

By creating a fresh SMTP client each time this will allow you to send out emails simultaneously.

Answer 3

Try this:

var client = new System.Net.Mail.SmtpClient("smtp.server");
var message = new System.Net.Mail.MailMessage() { /* provide its properties */ };
client.SendAsync(message, null);

Answer 4

The easiest Solution is to create a BackgroundWorker and push the mails into a queue. Then just let the BackgroundWorker go through the queue and send each mail.

See also How to: Run an Operation in the Background

Answer 5

Use the SmtpClient class and use the method SendAsync in the System.Net.Mail namespace.

Answer 6

What you want to do is run the e-mail task on a separate thread so the main code can continue processing while the other thread does the e-mail work.

Here is a tutorial on how to do that: Threading Tutorial C#