使用System.Net.Mail发送带有附件的电子邮件

Question

I am using System.Net.Mail to send emails through my application. I was trying to send emails with the attachments with following code.

    Collection<string> MailAttachments = new Collection<string>();
    MailAttachments.Add("C:\\Sample.JPG");
    mailMessage = new MailMessage();
    foreach (string filePath in emailNotificationData.MailAttachments)
    {
      FileStream fileStream = File.OpenWrite(filePath);
      using (fileStream)
       {
        Attachment attachment = new Attachment(fileStream, filePath);
        mailMessage.Attachments.Add(attachment);
       }
    }
     SmtpClient smtpClient = new SmtpClient();
     smtpClient.Host = SmtpHost;
     smtpClient.Send(mailMessage);

When I send the emails with the attachments it throw an exceptions as follows.

Cannot access a closed file.
at System.IO.__Error.FileNotOpen()
at System.IO.FileStream.Read(Byte[] array, Int32 offset, Int32 count)
at System.Net.Mime.MimePart.Send(BaseWriter writer)
at System.Net.Mime.MimeMultiPart.Send(BaseWriter writer)
at System.Net.Mail.Message.Send(BaseWriter writer, Boolean sendEnvelope)
at System.Net.Mail.MailMessage.Send(BaseWriter writer, Boolean sendEnvelope)
at System.Net.Mail.SmtpClient.Send(MailMessage message)

Answer 1

The ending curly brace of your using statement closes the file stream:

using (fileStream)
{
    Attachment attachment = new Attachment(fileStream, filePath);
    mailMessage.Attachments.Add(attachment);
}  // <-- file stream is closed here

However, the stream is read at the time of the stmpClient.Send(mailMessage) , where it is not open anymore.

The simplest solution is to provide just the file name instead of a stream:

Collection<string> MailAttachments = new Collection<string>();
MailAttachments.Add("C:\\Sample.JPG");

mailMessage = new MailMessage();
foreach (string filePath in emailNotificationData.MailAttachments)
{
    Attachment attachment = new Attachment(filePath);
    mailMessage.Attachments.Add(attachment);
}
SmtpClient smtpClient = new SmtpClient();
smtpClient.Host = SmtpHost;
smtpClient.Send(mailMessage);

With this solution, the .NET library will have to worry about opening, reading and closing the file.