C#自定义事件：属性改变引发事件示例

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

 namespace ConsoleApplication15
 {
     class Program
     {
         static void Main(string[] args)
         {
             Monitor m = new Monitor();
             m.PropertyChanging += new Monitor.EventHandler(m_PropertyChanging);
             m.Year = ;
             m.Year = ;
             m.Year = ;

         }

         static bool First=false;
         static void m_PropertyChanging(object sender, PropertyChangingEventArgs e)
         {
             if (First==false)
             {
                 First = true;
             }
             else
             {
                 if (e.NewValue <  || e.NewValue > )
                 e.Cancel = true;
             }
         }
     }

     //（属性正在改变的时候）事件数据
     class PropertyChangingEventArgs : EventArgs
     {
         //构造函数
         public PropertyChangingEventArgs(string PropertyName, int OldValue, int NewValue)
         {
             _PropertyName = PropertyName;
             _OldValue = OldValue;
             _NewValue = NewValue;
         }

         //存储数据
         private string _PropertyName;
         private int _OldValue;
         private int _NewValue;
         private bool _Cancel;

         //获取或设置属性
         public string PropertyName
         {
             set
             {
                 _PropertyName = value;
             }
             get
             {
                 return _PropertyName;
             }
         }
         public int OldValue
         {
             set
             {
                 _OldValue = value;
             }
             get
             {
                 return _OldValue;
             }
         }
         public int NewValue
         {
             set
             {
                 _NewValue = value;
             }
             get
             {
                 return _NewValue;
             }
         }
         public bool Cancel
         {
             set
             {
                 _Cancel = value;
             }
             get
             {
                 return _Cancel;
             }
         }
     }

     class Monitor
     {
         //定义委托
         public delegate void EventHandler(object sender, PropertyChangingEventArgs e);
         //定义事件
         public event EventHandler PropertyChanging;

         //事件处理（用属性方法）
         int _YearValue;
         public int Year
         {
             get
             {
                 return _YearValue;
             }
             set
             {
                 if (_YearValue != value)
                 {
                     if (PropertyChanging != null)
                     {
                         PropertyChangingEventArgs e = new PropertyChangingEventArgs("Year", _YearValue, value);
                         PropertyChanging(this, e);
                         if (e.Cancel)
                         {
                             return;
                         }
                         else
                         {
                             _YearValue = value;
                         }
                     }
                 }
             }
         }
     }

 }