Question

I am using SmtpClient to sent out email. I create some function in Mail class:

private void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
{
    // Get the unique identifier for this asynchronous operation.
    String token = (string)e.UserState;

    if (e.Cancelled)
    {
        MailStatus = Status.CANCEL;
        MailStatusMessage = token + " Send canceled.";
    }
    else if (e.Error != null)
    {
        MailStatus = Status.ERROR;
        MailStatusMessage = token + " " + e.Error.ToString();
    }
    else
    {
        MailStatus = Status.SENT;
        MailStatusMessage = "Mail sent.";
    }

    mailSent = true;
}

public void SentEmail()
{
    client = new SmtpClient(Host, Port);
    client.Credentials = new NetworkCredential(UserName, Password);
    MailAddress from = new MailAddress(MerchantEmail, MerchantName);
    MailAddress to = new MailAddress(CustomerEmail);
    MailMessage message = new MailMessage(from, to);
    message.Body = EmailSubjectTemplate();
    message.BodyEncoding = System.Text.Encoding.UTF8;
    message.Subject = EmailSubjectTemplate();
    message.SubjectEncoding = System.Text.Encoding.UTF8;

    client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);

    client.SendAsync(message, "Sending message.");

    message.Dispose();
}

In a form I call the function, before closing the form, but when waiting for the response from the SendCompletedCallback, the this.Close() will be executed:

Mail mail = new Mail();
mail.SentEmail();
this.Close();

How can I stop the form from closing before I get a response from SendCompletedCallback?

Answer 1

Option1

public class Mail 
{
    public delegate void MailSendComplete();
    public event MailSendComplete OnMailSendComplete;
    private void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
    {
        // your code 
        // finally call the complete event
        OnMailSendComplete();
    }

    public void SentEmail()
    {
        // your code 
    }
}

subscribe to this event from calling form as:

Mail m = new Mail();
m.OnMailSendComplete += new Mail.MailSendComplete(m_OnMailSendComplete);
m.SentEmail();

When you receive the complete event you can close the form
void m_OnMailSendComplete()
{
this.Close();
}

Option 2

when you create Mail object you can pass current form reference to it

Mail mail = new Mail(this);

then at the end of SendCompletedCallback you can close the form

public class Mail 
{
    public Form form { get; set; }
    public Mail(Form  f)
    {
        form = f;
    }

    private void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
    {
        // your code 
        // finally close the form
        form.Close();
    }
}