See Also: AttachmentCollection Members
Instances of the System.Net.Mail.AttachmentCollection class are returned by the MailMessage.AlternateViews and MailMessage.Attachments properties.
Use the MailMessage.AlternateViews property to specify copies of an e-mail message in different formats. For example, if you send a message in HTML, you might also want provide a plain text version in case some of the recipients use e-mail readers that cannot display HTML content.
Use the collection returned by the MailMessage.Attachments property to add an attachment, such as a file or the contents of a System.IO.Stream to this System.Net.Mail.MailMessage.