public MailMessage()
 {
     To         = new MailAddressCollection();
     Cc         = new MailAddressCollection();
     Bcc        = new MailAddressCollection();
     Attachment = new MailAttachmentCollection();
 }
        private void AddAttachments(System.Net.Mail.MailMessage mailMessage, MailAttachmentCollection attachments)
        {
            foreach (var attachment in attachments)
            {
                var contentBytes  = Convert.FromBase64String(attachment.AttachmentContent);
                var contentStream = new MemoryStream(contentBytes);

                var convertedAttachment =
                    new Attachment(
                        contentStream,
                        attachment.AttachmentName,
                        attachment.AttachmentType)
                {
                    TransferEncoding = TransferEncoding.Base64,
                };

                mailMessage.Attachments.Add(convertedAttachment);
            }
        }