如何解决TGIS在下面的编码错误?
未将对象引用设置到对象的实例。
public void totalprice()
{
int quantity;
float price;
float rowtotal ;
float subtotal=0;
float totalprice ;
foreach (GridViewRow row in GridView1.Rows)
{
//int pro_id = Convert.ToInt32(GridView1.DataKeys[row.RowIndex][0]);
quantity = Convert.ToInt32((row.FindControl("quantity")).ToString());
price = float.Parse((row.FindControl("price")).ToString());
rowtotal = quantity * price;
subtotal += rowtotal;
}
totalprice = subtotal;
lbltprice.Text = totalprice.ToString();
}