StringBuilder sb = new StringBuilder();

StringWriter stringWriter = new StringWriter(sb);

HtmlTextWriter htmlTextWriter = new HtmlTextWriter(stringWriter);

base.Render(htmlTextWriter);

string htmlText = sb.ToString();

writer.Write(htmlText);

byte[] htmlData = Encoding.Default.GetBytes(htmlText);

Attachment attachment = new Attachment(new MemoryStream(htmlData), "fileName.html");

// attach attachment to mail, send mail using smtpClient