I wanted to add an email attachment to a mail message that I was sending (when coding in ASP.Net). This tripped my up for a bit, but it turns out to be really easy. Turns out there is a method to do this on the MailMessage object. Here's how it's done:

-- Start by setting up your mail object. Yours may be different, but here's an example:

Dim objEmail as New MailMessage
objEmail.To = "someone@somecompany.com"
objEmail.FROM = "me@someothercompany.com"
objEmail.BODY = "some message"
etc, etc, etc

-- All that's needed to include the attachment is a call like this:

objEmail.Attachments.Add(new MailAttachment(server.MapPath("/path/to/myfile.txt")))