using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace 使用Object类实现后进先出队列
{
 class Stack
 {
  private Object[] _items;
  public Object[] Items
  {
   get { return this._items; }
   set { this._items = value; }
  }
  //将对象压入
  public void Push(Object obj)
  {
   //第一次压入时，进行初始化，长度为1
   if (this._items == null)
   {
    this._items = new Object[1];
    this._items[0] = obj;
   }
   else
   {
    int count = this._items.Length;
    Object[] objTemp = this._items;
    this._items = new Object[count + 1];
    int i = 0;
    foreach (Object o in objTemp)
    {
     this._items[i++] = o;
    }
    this._items[i] = obj;
   }
  }
  //按后入先出取出
  public Object Pop()
  {
   //为初始化或长度为0时，无法取出任何元素
   if (this._items == null||this._items.Length == 0)
    return null;
   else
   {
    Object obj = this._items[this._items.Length - 1];
    //删除最后一个元素
    this.DeleteLastObj();
    return obj;
   }
  }
  private void DeleteLastObj()
  {
   Object[] objTemp = new Object[this._items.Length - 1];
   for (int i = 0; i < this._items.Length - 1; i++)
   {
    objTemp[i] = this._items[i];
   }
   this._items = objTemp;
  }
 }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace 使用Object类实现后进先出队列
{
 public partial class Form1 : Form
 {
  public Form1()
  {
   InitializeComponent();
  }
  private Stack stack = new Stack();
  private Stack<string> stackGeneric= new Stack<string>();
  private void button1_Click(object sender, EventArgs e)
  {
   stack.Push(this.textBox1.Text);
  }
  private void button2_Click(object sender, EventArgs e)
  {
   Object[] objs = stack.Items;
   foreach(Object o in objs)
   {
    Console.WriteLine(o.ToString());
   }
  }
  private void button1_Click_1(object sender, EventArgs e)
  {
   try
   {
    Console.WriteLine(this.stack.Pop().ToString());
   }
   catch
   {
    Console.WriteLine("null");
   }
  }
  private void button3_Click(object sender, EventArgs e)
  {
   this.stackGeneric.Push(this.textBox2.Text);
  }
  private void button4_Click(object sender, EventArgs e)
  {
   try
   {
    Console.WriteLine(this.stackGeneric.Pop());
   }
   catch (InvalidOperationException)
   {
    Console.WriteLine("null");
   }
  }
 }
}