Asp.net 发送大量邮件超时的解决办法

我们知道在.Net中发送邮件使用的是SmtpClient 类，比如简单的如下：

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();

但是，如果在一个WebForm程序中，如果直接使用上述方法发送大量的邮件（比如：10000封），则必定要出现处理超时的错误提示。

解决办法：在需要发送邮件的时候，使用线程启动另外一个外部程序（比如一个命令行程序，执行完毕后自动关闭），而在这个外部程序中发送这些大量的邮件。这个外部程序可以参考上面发送邮件的代码。

protected void btnSend_Click(object sender, EventArgs e)
{
Session["ProcessRunning"] = "1";
ThreadStart start = new ThreadStart(RunSendMailProcess);
Thread t = new Thread(start);
t.Start();
Thread.Sleep(1000);
//启动一个页面进行提示
Page.RegisterStartupScript("newWindow", "<script>window.open('Progress.aspx', null, 'left=250,top=290,height=100,width=300,toolbar=no,status=no,menubar=no,location=center,scrollbars=no,resizable=no');</script>");
}

protected void RunSendMailProcess()
{
string arguments = @"""" + txtSubject.Text + @""" """ + txtBody.Text + @""" """ + txtSMTP.Text + @""" """ + txtFrom.Text + @""" """ + chkViaSql.Checked + @"""";

Process ps = new Process();
ps.StartInfo.CreateNoWindow = false;
ps.StartInfo.WorkingDirectory = System.Configuration.ConfigurationManager.AppSettings["SendMailPath"];
ps.StartInfo.WindowStyle = ProcessWindowStyle.Maximized;
ps.StartInfo.Arguments = arguments;
ps.StartInfo.FileName = "SendMail.exe";
ps.StartInfo.UseShellExecute = true;
ps.Start();
lock (Session.SyncRoot)
{
Session["ProcessRunning"] = "1";
}
ps.WaitForExit();
ps.Close();

lock (Session.SyncRoot)
{
Session["ProcessRunning"] = "0";
}
}