System.Net.Mail SmtpClient 类 异步方式发送电子邮件

     若要发送电子邮件并在等待电子邮件传输到 SMTP 服务器期间阻止其他操作，请使用一个同步 Send 方法。若要允许程序的主线程在传输电子邮件的过程中继续执行，请使用一个异步 SendAsync 方法。SendAsync 操作完成时会引发 SendCompleted 事件。若要接收此事件，必须将 SendCompletedEventHandler 委托添加到 SendCompleted 中。SendCompletedEventHandler 委托必须引用处理 SendCompleted 事件通知的回调方法。若要取消异步电子邮件传输，请使用 SendAsyncCancel 方法。

如果正在传输电子邮件时再次调用 SendAsync 或 Send，则会接收到 InvalidOperationException。

 

下面的代码示例演示如何以异步方式发送电子邮件。

C#

复制代码

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("[email protected]", "Jane " + (char)0xD8+ " Clayton", System.Text.Encoding.UTF8); // Set destinations for the e-mail message. MailAddress to = new MailAddress("[email protected]"); // 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."); } } }

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