如何使用网格视图值计算总价

public void totalprice()

   {

       float pricee;

       int quantityy;

      float totalprice;

       foreach (GridViewRow row in GridView1.Rows)

       {

           int pro_id = Convert.ToInt32(GridView1.DataKeys[row.RowIndex][0]);

           pricee = dal.getprice(pro_id);

           quantityy = dal.getquantity(pro_id);

           totalprice += quantityy * pricee;

       }

      lbltprice.Text = totalprice.ToString();

   }