Question

So I’ve been using System.Net.Mail.MailMessage objects for sending e-mail via SmtpClient for a while now. I noticed somewhere that MailMessage implements IDisposable, so I always use it within a using block.

using(MailMessage msg = new MailMessage())
{
    msg.To = blah... etc;
    ...
    smtpclient.Send(msg);
}

From metadata, you can see this info on the implementation of MailMessage

// Summary:
//     Releases all resources used by the System.Net.Mail.MailMessage.
[TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public void Dispose();
//
// Summary:
//     Releases the unmanaged resources used by the System.Net.Mail.MailMessage
//     and optionally releases the managed resources.
//
// Parameters:
//   disposing:
//     true to release both managed and unmanaged resources; false to release only
//     unmanaged resources.
protected virtual void Dispose(bool disposing);

But I’m wondering, why does MailMessage implement IDisposable? It does not appear to have anything to do with network-related items, because the SmtpClient handles all that.

Could it be due to potentially holding file handles for attached files? Is there something else there I’m forgetting?

Answer 1

According to dotPeek, it is disposing of its attachments and its views:

protected virtual void Dispose(bool disposing)
{
  if (!disposing || this.disposed)
    return;
  this.disposed = true;
  if (this.views != null)
    this.views.Dispose();
  if (this.attachments != null)
    this.attachments.Dispose();
  if (this.bodyView == null)
    return;
  this.bodyView.Dispose();
}