输入个人信息按年龄大小排列

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 结构体
{
class Program
{
struct tongji
{
public string xm;
public string sex;
public int old;
public double h;
public double tz;

}
static void Main(string[] args)
{

Console.Write("请输入人数：");
int a=int.Parse(Console.ReadLine());
ArrayList arr=new ArrayList();
for (int i = 0; i < a; i++)
{

tongji s = new tongji();
Console.WriteLine("正在输入第" + (i + 1) + "个人员信息");
Console.Write("请输入姓名：");
s.xm = Console.ReadLine();
Console.Write("请输入性别：");
s.sex = Console.ReadLine();
Console.Write("请输入年龄：");
s.old = int.Parse(Console.ReadLine());
Console.Write("请输入身高：");
s.h = double.Parse(Console.ReadLine());
Console.Write("请输入体重：");
s.tz = double.Parse(Console.ReadLine());
arr.Add(s);
}

for (int j = 0; j < a - 1; j++)
{
for (int k = j+1; k <a; k++)
{
if (((tongji)arr[j]).old > ((tongji)arr[k]).old)
{
tongji zhong = (tongji)arr[j];
arr[j] = arr[k];
arr[k] = zhong;

}
}
}
Console.Write("姓名\t性别\t年龄\t身高\t体重\n");
for (int p = 0; p < a; p++)
{
Console.Write(((tongji)arr[p]).xm + "\t" + ((tongji)arr[p]).sex + "\t" + ((tongji)arr[p]).old + "\t" + ((tongji)arr[p]).h + "\t" + ((tongji)arr[p]).tz + "\n");
}
Console.ReadLine();