关于一个计算总价的问题

public partial class Admin_Checkmoney : System.Web.UI.Page
{
DataTable orlist = new DataTable("cart");
DataRow prorow;
public Double oTotal = 0.0000;

protected void Page_Load(object sender, EventArgs e)
{
showorder();
}

private static string dbconnect()
{
return ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
}

protected void showorder()
{
if (Session["orderlist"] == null)
{
DataColumn[] keys = new DataColumn[1];
DataColumn a1 = new DataColumn("menu_id", typeof(string));
DataColumn a2 = new DataColumn("menu_name", typeof(string));
DataColumn a3 = new DataColumn("menu_price", typeof(decimal));
DataColumn a4 = new DataColumn("quantity", typeof(string));
DataColumn a5 = new DataColumn("subtotal", typeof(decimal));
orlist.Columns.Add(a1);
orlist.Columns.Add(a2);
orlist.Columns.Add(a3);
orlist.Columns.Add(a4);
orlist.Columns.Add(a5);
keys[0] = a1;
orlist.PrimaryKey = keys;
Session["orderlist"] = orlist;
}
else
{
orlist = (DataTable)Session["orderlist"];
}

}

protected void checking(object sender, EventArgs e)
{
bool same = true;
SqlCommand cmd = new SqlCommand("checkout", new SqlConnection(dbconnect()));
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("@o_name", SqlDbType.VarChar, 50);
cmd.Parameters["@o_name"].Value = this.oname.Text;
cmd.Connection.Open();
SqlDataReader dr = cmd.ExecuteReader();
if (!same)
{
if (dr.Read())
{
prorow = orlist.NewRow();
prorow["menu_id"] = dr["menu_id"].ToString();
prorow["menu_name"] = dr["menu_name"].ToString();
prorow["menu_price"] = dr["menu_price"].ToString();
prorow["quantity"] = dr["quantity"].ToString();
prorow["subtotal"] = Convert.ToInt32(dr[3].ToString()) * Convert.ToDecimal(dr[2].ToString());
orlist.Rows.Add(prorow);
}
}
Session["orderlist"] = orlist;
this.checkout.DataSource = dr;
this.checkout.DataBind();
cmd.Connection.Close();
}

protected void totalcount(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.Footer)
{
for (int i = 0; i < orlist.Rows.Count; i++)
{
oTotal += Convert.ToDouble(orlist.Rows[i][4]);
}
}
}
}
运行后 <%=oTotal %>的值是0，请各位帮我看看哪里出问题了啊。。