C#

try
        {
            SmtpClient client=new SmtpClient("smtp.gmail.com",587);
            MailMessage message = new MailMessage();
            message.From = new MailAddress(txtemail.Text);
            message.To.Add(txtreciever.Text);
            message.Body = txtbody.Text;
            message.Subject = txtsubject.Text;
            client.UseDefaultCredentials = false;
            client.EnableSsl = true;

            if (txtattachment.Text != "")
            {
                message.Attachments.Add(new Attachment(txtattachment.Text));

            }
            client.Credentials = new System.Net.NetworkCredential(txtemail.Text, txtpassword.Text);
            client.Send(message);
            message = null;
            MessageBox.Show("Message Sent");
        }
        catch(Exception ex)
        {
            MessageBox.Show( "Failed to Send Message");
        }

Hi,
I'm creating a C# dll which is going to be called from another c# application.
The dll task is to print documents.  It will queue the requests & print the docs 1 after another.

I would like the c# dll, once it has printed a doc, to notify the calling application.
Then a message will be displayed on the user's screen.

I'm trying to achieve this using Action<T> Delegate but can't get it to work.
What's the correct usage of Action<T> Delegate in both the dll & main application in this example?

Thanks