how to send email with attachment from local machine

using System.Net.Mail;

public partial class SUPER_mail : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button4_Click(object sender, EventArgs e)
    {
      
      
        MailMessage msg = new MailMessage();
        msg.From = new MailAddress("your gmail id");
        msg.To.Add(TextBox2.Text);
        msg.Subject = TextBox3.Text;
        msg.Body = TextBox4.Text;
 if (FileUpload1.HasFile)
        {
            FileUpload1.SaveAs("C:\\Program Files (x86)\\Common Files\\microsoft shared\\DevServer\\10.0\\" + FileUpload1.FileName);
            Label3.Text = FileUpload1.FileName;
  msg.Attachments.Add(new Attachment(Label3.Text));
        }

     
        SmtpClient smt = new SmtpClient();
        smt.Send(msg);
        Label2.Text = "mail sucessfully transfer";
    }
}

//inside the web.config file

<system.net >
    <mailSettings >
      <smtp >
        <network host ="smtp.gmail.com"  password ="your gmail password" userName ="your gmail id"/>
      </smtp>
    </mailSettings>
  </system.net>