如何从回调方法返回值 [英] How do I return value from callback method

问题描述

我使用此代码在asp.net中发送电子邮件。这个方法是在class.i想要在发送完成时保存电子邮件信息。如果发送返回true，如果发生错误，则可以从此方法返回一个值到页面返回false.then代码在页面保存电子邮件信息？

提前谢谢你。

i use this code to send email in asp.net.this methos is in class.i want to save email info when send completed.how can return a value from this method to page that if send return true,if error occured return false.then code in page save email info?
thank you in advance.

public void SendAsyncMail()
{
    MailMessage mail = new MailMessage();

    mail.From = new MailAddress("Enter from mail address");
    mail.To.Add(new MailAddress("Enter to address #1"));
    mail.To.Add(new MailAddress("Enter to address #2"));
    mail.Subject = "Enter mail subject";
    mail.Body = "Enter mail body";

    SmtpClient smtpClient = new SmtpClient();
    Object state = mail;

    //event handler for asynchronous call
    smtpClient.SendCompleted += new SendCompletedEventHandler(smtpClient_SendCompleted);
    try
    {
        smtpClient.SendAsync(mail, state);
    }
    catch (Exception ex) { /* exception handling code here */ }
}

void smtpClient_SendCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
{
    MailMessage mail = e.UserState as MailMessage;

    if (!e.Cancelled && e.Error!=null)
    {
        message.Text = "Mail sent successfully";
    }
}

推荐答案

实现此目的的一种方法是覆盖 AsyncCompletedEventArgs 并实现自己的返回方法。

例如

One approach to achieve this is to override AsyncCompletedEventArgs and implement your own return methods.
For e.g.

public class CalculatePrimeCompletedEventArgs :
    AsyncCompletedEventArgs
{
public CalculatePrimeCompletedEventArgs(
     ...)
    {
        //Do stuff
    }
}

完整示例，请尝试如何：实现支持基于事件的异步模式的组件 [ ^ ]。

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