How to know, that email was sent, and attachments can be deleted?

Question

I have a method, which saves screenshot by the definite path and then makes email message, attaching screenshot to it. As I've understood, after sending it - the special thread is being created in which attachment file is used, so I can't delete it while that thread is working. So, I need to know if when the file will be accessible for deleting.

Here's my code:

-- Configuring smtp

private SmtpClient CreateSMTP()
{
    var smtp = new SmtpClient("gate");
    smtp.UseDefaultCredentials = false;
    smtp.Credentials = new NetworkCredential("notifications@****.com", "3eCMCQxFde");
    smtp.Port = 25;
    smtp.EnableSsl = false;

    return smtp;
}

-- Making message

public MailMessage MakeMessage(bool screenshotFlag)
    {
        MailAddress from = new MailAddress("notifications@****.com", Name);
        MailAddress to = new MailAddress("****@****.com");
        MailMessage message = new MailMessage(from, to);

        message.Subject = Subject == string.Empty ? string.Empty : Subject;
        message.Body = MessageText;
        message.Body = GenerateLogAndExceptionInfo(message.Body);
        message.BodyEncoding = Encoding.Unicode;

        message.ReplyTo = new MailAddress(Mail);

        if (screenshotFlag)
        {
            CreateScreenshot();
            message.Attachments.Add(new Attachment(MailHelper.FeedBackScreenShotPath));
        }

        return message;
    }

-- Sending email

public void SendMessage()
{
    using (SmtpClient smtp = CreateSMTP())
    {
        smtp.Send(MakeMessage(SendWithScreenshot));
    }
}

Deleting is realized before closing the app. But if I send message and then close the program very quickly - the attached file is still being used by "sending thread" , so I have an exception. Before deleting I need to know exactly if file is not used anymore. @DenisSchaf — Харламов Даниил, Mar 11 '19 at 09:29
If it is a user related problem, like the user is closing the app, then on the close button, just hide your form/interface and finish sending the email before deleting the attachments and closing the app. — meJustAndrew, Mar 11 '19 at 09:31
Yes, I want to hide interface, or wait, or deny closing the app. But I don't know if when email is really sent. @meJustAndrew — Харламов Даниил, Mar 11 '19 at 09:39
You could see [this thread](https://stackoverflow.com/questions/10504647/deleting-files-in-use) for waiting after the file is not in use anymore and then delete it. — meJustAndrew, Mar 11 '19 at 10:10

Patrick Hofman · Accepted Answer · 2019-03-11T10:18:10.683

2

From the documentation:

These methods block while the message is being transmitted.

So while the message is being transmitted, the method blocks. So after the method is done and you've disposed the message instance, you could delete the file.

Of course, it could still have a lock on the file. That is why I would say you should first dispose the SmtpClient and then try to delete the file (so do that after the using block). It should be fine then.

edited Mar 11 '19 at 10:18

answered Mar 11 '19 at 09:26

Patrick Hofman

153,850
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249
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Didn't help. After Using block I have some more code, and it works, but in parallel to sending. I mean that the ending of Using block doesn't guarantee, that the mail was sent, or the file is not used anymore. – Харламов Даниил Mar 11 '19 at 09:36
Yes, it does. The end of the `using` block guarantees the mail has been delivered to the sending server. It is not used by .NET any more. – Patrick Hofman Mar 11 '19 at 09:41
So, the problem is not in parallel sending? I mean that smtp isn't holding the file after Using block, but Windows is? – Харламов Даниил Mar 11 '19 at 09:44
What is that parallel sending you are talking about? You don't show any parallelism in your sample code. – Patrick Hofman Mar 11 '19 at 09:45
These are just my thoughts. Now I've tried to Sleep(1000) in Using block after sending, and after Using block - deleting file. But it's still in use( – Харламов Даниил Mar 11 '19 at 09:48
@ХарламовДаниил What is wrong with my answer that you unaccepted? – Patrick Hofman Mar 11 '19 at 13:58
Because I've wanted to check my answer, which helped. For other people. But I checked yours by accident) Nothing personal) – Харламов Даниил Mar 11 '19 at 14:30
But if you really want, I can recheck) – Харламов Даниил Mar 11 '19 at 14:33
If you want, you should. If you don't, don't. – Patrick Hofman Mar 11 '19 at 14:33
(Btw, I added "disposed the message instance" in my answer to fix that part) – Patrick Hofman Mar 11 '19 at 14:34

score 0 · Answer 2 · answered Mar 11 '19 at 10:15

0

I've seen that the file was holding by the message object, not by smtp object, so I added using block for message, too.

Thanks to all))

answered Mar 11 '19 at 10:15

Харламов Даниил

163
1
10

How to know, that email was sent, and attachments can be deleted?

2 Answers2