用ASP.NET编写一程序，求出1—5阶乘之和并显示

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace WebApplication2
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Sum();
}
}
private static int sum = 0;
private void Sum()
{
int minNumber = 1;
int maxNumber = 5;
for (int i = minNumber; i <= maxNumber; i++)
{
for (int j = minNumber; j <= i; j++)