在C#中使用代理的方式触发事件 的简单习作

程序简单就 不再作说明了.
在学习IssueVision的OBSERVER(观察者)模式时由于对代理和事件不是很熟悉,遇到了一些问题,所以就有了这个简单习作.
TestEvent.cs

using System;

namespace ConsoleApplication2
{
    /// <summary>
    /// Class1 的摘要说明。
    /// </summary>
    class TestEvent
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            //
            // TODO: 在此处添加代码以启动应用程序
            //

            TestEvent c = new TestEvent();
            c.Test();
       
        }

        public void Test()
        {
            ChangeNumber number = new ChangeNumber();
 
            number.BigEvent += new ChangeNumber.ChangeHandler(this.Big);
            number.SmallEvent += new ChangeNumber.ChangeHandler(this.Small);
            number.EqualEvent += new ChangeNumber.ChangeHandler(this.Equal);

            number.Number = 1;        //运行之前Number=0;
            number.Number = 1;        //运行之前Number=1;
            number.Number = 0;        //运行之前Number=1;
        }

        public void Big()
        {
            Console.WriteLine("big");
        }
        public void Small()
        {
            Console.WriteLine("small");
        }
        public void Equal()
        {
            Console.WriteLine("equal");
        }
    }
}

ChangeNumber.cs

using System;

namespace ConsoleApplication2
{
    /// <summary>
    /// Class2 的摘要说明。
    /// </summary>
    public class ChangeNumber
    {
        public delegate void ChangeHandler();

        public event ChangeHandler BigEvent;
        public event ChangeHandler SmallEvent;
        public event ChangeHandler EqualEvent;

        public ChangeNumber()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        private int m_number = 0;

        public int Number
        {
            set
            {
                if(value > this.m_number)
                {
                    BigEvent();            //这时最好先判断一下BigEvent是不是为null
                }
                else if(value < this.m_number)
                {
                    SmallEvent();
                }
                else
                {
                    EqualEvent();
                }

                m_number = value;
            }
        }
    }
}