编辑代码

using System;

public class Stack
{
    int position;
    object[] data = new object[10];
    public void Push (object obj)   { data[position++] = obj;  }
    public object Pop()               { return data[--position]; }
}

public class HelloWorld
{
    public static void Main()
    {
        // Stack stack = new Stack();
        // stack.Push ("sausage");
        // string s = (string) stack.Pop();    // Downcast, so explicit cast is needed
        // Console.WriteLine (s);              // sausage

        // 装箱和拆箱
        int i = 3;
        object boxed = i;
        i = 5;
        i = (int)boxed;           // Unbox the int;
        Console.WriteLine (boxed);     // 3
        Console.WriteLine (i);
    }
}