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

namespace array
{
    class Program
    {
        static void Main(string[] args)
        {
            int i;
            
            Random rd = new Random(DateTime .Now .Second );
            ArrayList alist = new ArrayList();
            for (i = 0; i < 20; i++)
            {
                alist.Add(rd.Next (60,100));
                if (i % 10 == 0)
                {
                    alist.Add('\n');
                }
            }
            foreach (object ob in alist)
            {
                 Console.Write("{0,4}",ob );
            }
            alist.Sort();
            for (int j = 0; j < alist.Count; j++)
            {
                alist .Add (alist[j ]);
            }
            foreach (object obj in alist)
            {
                Console.Write("{0,4}", obj);
            }
           
            Console.Read();
        }
    }
}

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

namespace array
{
    class Program
    {
        static void Main(string[] args)
        {
            int i;

            Random rd = new Random(DateTime.Now.Second);
            ArrayList alist = new ArrayList();
            for (i = 0; i < 20; i++)
            {
                alist.Add(rd.Next(60, 100));
                //ArrayList中既含有数字，又含有字符，是不能排序的，数字和字符无法比较
                //if (i % 10 == 0)
                //{
                //    alist.Add('\n');
                //}
            }
            foreach (object ob in alist)
            {
                Console.Write("{0,4}", ob);
            }
            alist.Sort();
            //排完序以后，alist里面的值已经是排完序以后的状态，排序以前的顺序已经没有了
            //for (int j = 0; j < alist.Count; j++)
            //{
            //    alist.Add(alist[j]);
            //}
            foreach (object obj in alist)
            {
                Console.Write("{0,4}", obj);
            }
            Console.Read();
        }
    }
}

这是昨天新教的内容，我们老师讲的有点快，知识点就没get到，谢啦，亲爱的版主大大。。。

按照老师的要求和版主的帮助，润色了一下
ArrayList应用：产生随机数排序并输出
（1）随机产生20个整数，在60-100之间，加入ArrayList对象中；
（2）每行10个数据，输出这些随机数；
（3）从小到大排序，输出排序后的随机数。
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace array
{
    class Program
    {
        static void Main(string[] args)
        {
            int i,count=0;
            Random rd = new Random(DateTime.Now.Second);
            ArrayList alist = new ArrayList();
            for (i = 0; i < 20; i++)
            {
                alist.Add(rd.Next(60, 100));                           
            }
            foreach (object ob in alist)
            {
                Console.Write("{0,4}", ob);
                count ++;
                if (count % 10 == 0)
                {
                    Console.WriteLine();
                }
            }
            alist.Sort();
            Console.WriteLine("排序后的数为：");
            foreach (object obj in alist)
            {            
                Console.Write("{0,4}", obj);
                count++;
                if (count % 10 == 0)
                {
                    Console.WriteLine();
                }
            }
             Console.Read();
        }
    }
}