private void setSLVatTu()
        {
            //txtSL.Text = "-";

            //chkboxXacNhanXuat == true
            Double sl;
            if (chkboxXacNhanXuat.Checked == true && Double.TryParse(txtSL.Text.Trim().ToString(), out sl) == true)
            {
                reset_txtSL();
                return;
            }

            //Check ID Kho
            int ID_kho = getIDKho();
            if (getIDKho() < 0)
            {
                reset_txtSL();
                return;
            }

            //Check VT
            if (cbMaVatTu.SelectedIndex == -1)
            {
                reset_txtSL();
                return;
            }

            //Check Chất Lượng
            if (cbChatLuong.SelectedIndex == -1)
            {
                reset_txtSL();
                return;
            }

            string Ma_vat_tu = cbMaVatTu.GetItemText(cbMaVatTu.SelectedItem); //cbMaVatTu.SelectedText.ToString(); //cbMaVatTu.Text.Trim().ToString();
            int Id_chat_luong = Int32.Parse(cbChatLuong.SelectedValue.ToString());

            clsTonKho TonKho = new clsTonKho();
            Double SL = TonKho.getSL(Ma_vat_tu, ID_kho, Id_chat_luong);

            txtSL.Text = SL.ToString();
        }