如何从ASP.NET MVC中的SQL Server数据库向多个收件人发送电子邮件？

Question

I want to send email to multiple recipients. I retrieve the email addresses of multiple users from a SQL Server database, like this:

var students = (from u in db.Users
                where u.projectGroup == id
                select u.userEmail).ToArray();

This will return multiple email addresses like: user1@gmail.com user2@gmail.com and I try to send to multiple users like this

for (int h = 0; h < students.Length; h++)
{
    try
    {
        var body = "<p>Email From: {0} ({1})</p><p>Message:</p><p>{2}</p>";
        var smtpClient = new SmtpClient();

        var message = new MailMessage();
        message.To.Add(new MailAddress(students[h])); 
        message.Subject = "I'm interested in your project";
        message.Body = string.Format(body, model.FromName, model.FromEmail, model.Message);
        message.IsBodyHtml = true;

        using (var smtp = new SmtpClient())
        {
            await smtp.SendMailAsync(message);
            return RedirectToAction("Sent");
        }
    }
    catch (Exception ex)
    {
        //MessageBox("Your Email address is not valid");
        //ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('Your Email address is not valid');", true);
    }
}

but this did not work, it sends an email to first user but another user did not receive the email.

How can I split each email in a one row to send an email to multiple recipients?

Answer 1

Everything seems to be good. However, your redirectToAction is executing for the first email and comes out of loop.After that control doesn't know how to continue for second record. that's why your email wont be sent to second email. try below code you should be good.

for (var index= 0; index< students.Length; index++)
    {
        try
        {
            var body = "<p>Email From: {0} ({1})</p><p>Message:</p><p>{2}</p>";
            var smtpClient = new SmtpClient();

            var message = new MailMessage();
            message.To.Add(new MailAddress(students[index])); 
            message.Subject = "I'm interested in your project";
            message.Body = string.Format(body, model.FromName, model.FromEmail, model.Message);
            message.IsBodyHtml = true;

            using (var smtp = new SmtpClient())
            {
                await smtp.SendMailAsync(message);
                       }
        }
        catch (Exception ex)
        {
            //MessageBox("Your Email address is not valid");
            //ScriptManager.RegisterStartupScript(this, this.GetType(), "popup", "alert('Your Email address is not valid');", true);
        }
    }

     return RedirectToAction("Sent");

Answer 2

return RedirectToAction("Sent"); is the culprit.

This will stop your code after the first email. Don't return from your method until they've all been sent:

using (var smtp = new SmtpClient())
{
  for (int h = 0; h < students.Length; h++)
  {
    var body = "<p>Email From: {0} ({1})</p><p>Message:</p><p>{2}</p>";

    var message = new MailMessage();
    message.To.Add(new MailAddress(students[h])); 
    message.Subject = "I'm interested in your project";
    message.Body = string.Format(body, model.FromName, model.FromEmail, model.Message);
    message.IsBodyHtml = true;

    smtp.Send(message);
  }
}
return RedirectToAction("Sent");

NB I also removed the redundant try/catch (don't use it if you're not going to log the exception (although you should do that globally anyway), suppressing unexpected errors is an anti-pattern) and reduced the number of times you unnecessarily instantiate a brand new SmtpClient - it's fine to use the same one each time. Also, if you're going to await the async email call, there's no point using it - just use the regular Send instead.

Answer 3

您是从循环内部返回SENT，因此它执行第一个项目然后退出。