how to calculate the Net total from gridview or datatable to but it in label?

protected void btnUpdate_Click1(object sender, EventArgs e)
  {

     // try
      //{
          for (int i = 0; i < GridView2.Rows.Count; i++)
          {
              TextBox Tb = (TextBox)GridView2.Rows[i].FindControl("TextBoxCount");
              Basket_DataTable.Rows[i]["count"] = Tb.Text;
              Basket_DataTable.Rows[i]["Total"] = Convert.ToInt32(Tb.Text) * Convert.ToInt32(Basket_DataTable.Rows[i]["SellingPrice"]);
          }