send email

  MailMessage message = new MailMessage();
            message.From = new MailAddress("lanzy519@163.com");
            message.To.Add(new MailAddress(TextBox_receive.Text));
            message.Subject = TextBox_title.Text;
            message.Priority = MailPriority.High;
            message.Body = TextBox_body.Text.Replace ("\n","<br>");

            if ((string)FileUpload1.FileName != "")
            {
                if (FileUpload1.FileContent.Length / 1024 < 41)
                {
                    string filname = Server.MapPath("attachment") + "\\" + FileUpload1.FileName;
                    FileUpload1.SaveAs(filname);
                  
                    message.Attachments.Add(new Attachment(filname));
                    message.BodyEncoding = System.Text.Encoding.UTF8;
                    message.IsBodyHtml = true;
                  //  message.ToString().Replace("<br>", "\n");
                    SmtpClient sendmail = new SmtpClient();

                    sendmail.Send(message );

                    Response.Write("<script language=javascript  defer>alert('发送成功')</script>");
                    
                   
                }
                else
                {
                    Response.Write("<script language=javascript  defer >alert('文件大与40K')</script>");


                }
            }

            else {

                message.BodyEncoding = System.Text.Encoding.UTF8;
                message.IsBodyHtml = true;
                SmtpClient sendmail = new SmtpClient();

                sendmail.Send(message);

                message.Dispose();
                
                Response.Write("<script language=javascript  defer >alert('发送成功')</script>");
            }

        }
        catch (Exception  ex)
        {
            Response.Write("<script language=javascript  defer >alert("+ex .Message +")</script>");
        }
    }