在C＃中異步發送電子郵件？

Question

我正在開發一個應用程序，用戶點擊/按下窗口中的某個按鈕，應用程序會執行一些檢查並確定是否發送一些電子郵件，然後用消息顯示另一個窗口。

我的問題是，發送2封電子郵件顯着降低了處理速度，並且對於某些（〜8）秒，第一個窗口在發送時會凍結。

有沒有什麼辦法讓我可以在後臺發送這些電子郵件並立即顯示下一個窗口？

請不要用「使用X類」或「只使用X方法」來限制您的答案，因爲我對語言還不是太熟悉，而且還有一些更多的信息會受到高度讚賞。

謝謝。

Answer 1

從.NET 4.5開始，SmtpClient實現了異步等待方法 SendMailAsync。 其結果是，異步發送電子郵件如下：

public async Task SendEmail(string toEmailAddress, string emailSubject, string emailMessage) 
{ 
    var message = new MailMessage(); 
    message.To.Add(toEmailAddress); 

    message.Subject = emailSubject; 
    message.Body = emailMessage; 

    using (var smtpClient = new SmtpClient()) 
    { 
     await smtpClient.SendMailAsync(message); 
    } 
} 

Answer 2

，這不是太複雜，只需發送一個單獨的線程消息：

using System.Net.Mail; 

Smtp.SendAsync(message); 

或者，如果你想建立的獨立的線程，而不是整個消息，而只是將其發送異步：

using System.Threading; 
using System.Net.Mail; 

var sendMailThread = new Thread(() => { 
    var message=new MailMessage(); 
    message.From="from e-mail"; 
    message.To="to e-mail"; 
    message.Subject="Message Subject"; 
    message.Body="Message Body"; 

    SmtpMail.SmtpServer="SMTP Server Address"; 
    SmtpMail.Send(message); 
}); 

sendMailThread.Start(); 

Answer 3

你想要做的就是在一個單獨的線程上運行電子郵件任務，這樣主代碼可以繼續處理，而另一個線程完成電子郵件的工作。

這裏是如何做到這一點的教程： Threading Tutorial C#

Answer 4

SmtpClient.SendAsync Method

樣品

using System; 
using System.Net; 
using System.Net.Mail; 
using System.Net.Mime; 
using System.Threading; 
using System.ComponentModel; 
namespace Examples.SmptExamples.Async 
{ 
    public class SimpleAsynchronousExample 
    { 
     static bool mailSent = false; 
     private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e) 
     { 
      // Get the unique identifier for this asynchronous operation. 
      String token = (string) e.UserState; 

      if (e.Cancelled) 
      { 
       Console.WriteLine("[{0}] Send canceled.", token); 
      } 
      if (e.Error != null) 
      { 
       Console.WriteLine("[{0}] {1}", token, e.Error.ToString()); 
      } else 
      { 
       Console.WriteLine("Message sent."); 
      } 
      mailSent = true; 
     } 
     public static void Main(string[] args) 
     { 
      // Command line argument must the the SMTP host. 
      SmtpClient client = new SmtpClient(args[0]); 
      // Specify the e-mail sender. 
      // Create a mailing address that includes a UTF8 character 
      // in the display name. 
      MailAddress from = new MailAddress("jane@contoso.com", 
       "Jane " + (char)0xD8+ " Clayton", 
      System.Text.Encoding.UTF8); 
      // Set destinations for the e-mail message. 
      MailAddress to = new MailAddress("ben@contoso.com"); 
      // Specify the message content. 
      MailMessage message = new MailMessage(from, to); 
      message.Body = "This is a test e-mail message sent by an application. "; 
      // Include some non-ASCII characters in body and subject. 
      string someArrows = new string(new char[] {'\u2190', '\u2191', '\u2192', '\u2193'}); 
      message.Body += Environment.NewLine + someArrows; 
      message.BodyEncoding = System.Text.Encoding.UTF8; 
      message.Subject = "test message 1" + someArrows; 
      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, the userToken is a string constant. 
      string userState = "test message1"; 
      client.SendAsync(message, userState); 
      Console.WriteLine("Sending message... press c to cancel mail. Press any other key to exit."); 
      string answer = Console.ReadLine(); 
      // If the user canceled the send, and mail hasn't been sent yet, 
      // then cancel the pending operation. 
      if (answer.StartsWith("c") && mailSent == false) 
      { 
       client.SendAsyncCancel(); 
      } 
      // Clean up. 
      message.Dispose(); 
      Console.WriteLine("Goodbye."); 
     } 
    } 
} 

Answer 5

最簡單的解決方案是創建一個BackgroundWorker和推郵件到隊列中。然後，讓BackgroundWorker通過隊列併發送每封郵件。

又見How to: Run an Operation in the Background

Answer 6

使用SmtpClient類和使用方法​​在System.Net.Mail命名空間。

Answer 7

只是因爲這是一個有點含糊......我將簡要...

有很多方法可以做到同步或並行工作，在C＃/。NET等

最快方法來做你想做的就是使用後臺工作線程，這將避免鎖定你的用戶界面。

與後臺工作線程提示：你不能直接從他們更新UI（線程親和力和編組站只是你要學會處理事情...）

另一個要考慮的......如果你使用標準的System.Net.Mail類型的東西來發送電子郵件......要小心你如何制定你的邏輯。如果你用某種方法將其全部隔離並反覆調用，那麼每次都可能不得不拆卸並重建與郵件服務器的連接，並且認證等所涉及的延遲仍會使整個事件不必要地減速。在可能的情況下，通過單個打開的連接向郵件服務器發送多個電子郵件。

Answer 8

試試這個：

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

Answer 9

使用.NET 4.0的Task Parallel Library，你可以這樣做：

Parllel.Invoke(() => { YourSendMailMethod(); }); 

而且，看到cristina manu's博客帖子大約Parallel.Invoke（）與明確的任務管理。

Answer 10

由於它是一個小的工作單元，因此它應該使用ThreadPool.QueueUserWorkItem作爲它的線程方面。如果您使用SmtpClient類發送郵件，則可以處理SendCompleted事件以向用戶提供反饋。

ThreadPool.QueueUserWorkItem(t => 
{ 
    SmtpClient client = new SmtpClient("MyMailServer"); 
    MailAddress from = new MailAddress("me@mydomain.com", "My Name", System.Text.Encoding.UTF8); 
    MailAddress to = new MailAddress("someone@theirdomain.com"); 
    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(); 
} 

通過創建一個新的SMTP客戶端，每次這將允許您同時發送電子郵件。

Answer 11

這裏是一個火災和使用的.Net 4.5.2+異步一起忘記的方法：

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

其中BackgroundTaskRunner是：

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 
      } 
     }); 
    } 
} 

像Azure App Services上的魅力一樣工作。