private void TxtNumberSub_Validating(object sender, CancelEventArgs e)
 {
     if (!string.IsNullOrEmpty(txtSubPackage.Text))
     {
         if (string.IsNullOrEmpty(txtNumberSub.Text))
         {
             e.Cancel = true;
             errorProvider.SetError(txtNumberSub, "Please input number of sub package");
         }
         else if (!ProDAO.checkInt(txtNumberSub.Text) || int.Parse(txtNumberSub.Text) <= 0)
         {
             e.Cancel = true;
             errorProvider.SetError(txtNumberSub, "Number sub package must be number and greater than 0");
         }
         else
         {
             e.Cancel = false;
             errorProvider.SetError(txtNumberSub, null);
         }
     }
     else
     {
         e.Cancel = false;
         errorProvider.SetError(txtNumberSub, null);
     }
 }
        //validate
        public bool validate()
        {
            bool valid = true;

            if (string.IsNullOrEmpty(txtNumberPackage.Text))
            {
                errorProvider.SetError(txtNumberPackage, "Please input number of one package");
                valid = false;
            }
            else if (!ProDAO.checkInt(txtNumberPackage.Text) || int.Parse(txtNumberPackage.Text) < 0)
            {
                errorProvider.SetError(txtNumberPackage, "Number package must be possible number");
                valid = false;
            }
            else if (!string.IsNullOrEmpty(lbSub.Text))
            {
                errorProvider.SetError(txtNumberPackage, null);
                if (string.IsNullOrEmpty(txtNumberSub.Text))
                {
                    valid = false;
                    errorProvider.SetError(txtNumberSub, "Please input number of sub package");
                }
                else if (!ProDAO.checkInt(txtNumberSub.Text) || int.Parse(txtNumberSub.Text) < 0)
                {
                    valid = false;
                    errorProvider.SetError(txtNumberSub, "Number sub package must be number and greater than 0");
                }
                else
                {
                    valid = true;
                    errorProvider.SetError(txtNumberSub, null);
                }
            }
            else
            {
                valid = true;
                errorProvider.SetError(txtNumberPackage, null);
                errorProvider.SetError(txtNumberSub, null);
            }
            return(valid);
        }