Question : How can I get an email to release its hold on an attachment after sending?

I am using a System.Net.Mail.MailMessage to send email messages with attachments - that all works fine. However, after the mail has been sent the attached item is still marked as in use and therefore a temporary file created specifically for the attachment cannot be deleted - the error message 'File is in use by another process' is displayed when the system attempts to remove it.

How can I ensure that the lock is released once the message has been sent?

Chris Bray

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// Add any attachments
                if (attachmentsListView.Items.Count > 0)
                {
                    foreach (ListViewItem AttachmentItem in attachmentsListView.Items)
                    {
                        Attachment attach = new Attachment(AttachmentItem.Tag.ToString());
                        message.Attachments.Add(attach);
                    }
                }

Answer : How can I get an email to release its hold on an attachment after sending?

I think in your code you are disposing the message; not individual attachment objects...try the change below :

private void EmailDialog_FormClosing(object sender, FormClosingEventArgs e)
{

foreach (Attachment a in message.Attachments)
a.Dispose();

message.Attachments.Clear();
message.Dispose();
message = null;
if (iconImageList != null)
iconImageList.Dispose();
}