Question

I’ve tried following this link Asynchronous call but some classes are obsolete.
So I want an exact answer for my project.

public class RegisterInfo
{
    public bool Register(UserInfo info)
    {
        try
        {
            using (mydatabase db = new mydatabase())
            {
                userinfotable uinfo = new userinfotable();
                uinfo.Name = info.Name;
                uinfo.Age = info.Age;
                uinfo.Address = info.Address;

                db.userinfotables.AddObject(uinfo);
                db.SaveChanges();

                // Should be called asynchronously
                Utility.SendEmail(info); // this tooks 5 to 10 seconds or more.

                return true;
            }
        }
        catch { return false; }
    }
} 

public class UserInfo
{
    public UserInfo() { }

    public string Name { get; set; }
    public int Age { get; set; }
    public string Address { get; set; }
}  

public class Utility
{
    public static bool SendEmail(UserInfo info)
    {
        MailMessage compose = SomeClassThatComposeMessage(info);
        return SendEmail(compose);
    }

    private static bool SendEmail(MailMessage mail)
    {
        try
        {
            SmtpClient client = new SmtpClient();
            client.Host = "smtp.something.com";
            client.Port = 123;
            client.Credentials = new System.Net.NetworkCredential("[e-mail]", "password");
            client.EnableSsl = true;

            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(ValidateServerCertificate);
            client.Send(mail);

            return true;
        }
        catch { return false; }
    }
}    

Please look at the Register method.
After saving the data, I don’t want to wait for the sending of mail. If possible I want to process the sending of mail on other thread so the user will not wait for a longer time.
I don’t need to know if mail has sent successfully.
Hope you could understand what I mean. Sorry for my bad English.

Answer 1

Using Thread:

new Thread(() => Utility.SendEmail(info)).Start();

Using ThreadPool:

ThreadPool.QueueUserWorkItem(s => Utility.SendEmail(info));

Using Task:

Task.Factory.StartNew(() => Utility.SendEmail(info));

Of course Thread and ThreadPool require using System.Threading while Task requires using System.Threading.Tasks

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As stated by David Anderson, SmtpClient already supports asynchronous send ^{(I probably should have paid attention to the content of the function rather than answering the question)}, so technically you could just use that to handle the send though it won’t offload the processing of your entire method.