hi any body please help me about the following error

MailMessage msgMail = new MailMessage();
        msgMail.To = TextBox3.Text;
        msgMail.From = "abc@gmail.com";
        msgMail.Subject = "Attachment Test";

        msgMail.BodyFormat = MailFormat.Text;
        msgMail.Body = "Name:" + txtName.Text + "\n" + "Designation:" +                                        DropDownList1.Value + "\n" + " Phone No:" + TextBox2.Text;
        String strPath = Path.GetFullPath(MyFile.PostedFile.FileName);
        msgMail.Attachments.Add(new MailAttachment(strPath));
        SmtpMail.Send(msgMail);
        Response.Write("Email was queued to disk");