写一个类时，有时候会在同一个类上添加很多事件，事件很多的话，是不容易管理的，.NET提供的EventHandlerList可以辅助多个事件的管 理，但不方便的地方是，它不是类型安全的,缺少类型安全，多少用起来担心会出错。经过改造，可以将系统提供的EventHandlerList通 过泛型提供类型安全的管理。泛型类EventHandlerList.cs的实现如下：

public sealed class EventHandlerList
     
       : IDisposable     {         ListEntry head;        public EventHandlerList()         { }        public Delegate this[T key]        {            get{                 ListEntry e = Find(key);                return e == null ? null : e.m_handler;            }            set{                ListEntry e = Find(key);                if (e != null){                    e.m_handler = value;                }                 else {                    head = new ListEntry(key, value, head);                }            }        }        public void AddHandler(T key, Delegate value)         {            ListEntry e = Find(key);             if (e != null) {                e.m_handler = Delegate.Combine(e.m_handler, value);            }            else {                 head = new ListEntry(key, value, head);            }         }         public void AddHandlers(EventHandlerList
      
        listToAddFrom)         {            ListEntry currentListEntry = listToAddFrom.head;            while (currentListEntry != null) {                 AddHandler(currentListEntry.m_key, currentListEntry.m_handler);                currentListEntry = currentListEntry.m_next;             }         }         public void Dispose()         {             head = null;        }          private ListEntry Find(T key)         {            ListEntry found = head;             while (found != null) {                if (found.m_key.Equals(key)) {                    break;                }                 found = found.m_next;            }             return found;         }         public void RemoveHandler(T key, Delegate value)         {            ListEntry e = Find(key);             if (e != null) {                e.m_handler = Delegate.Remove(e.m_handler, value);            }         }         private sealed class ListEntry         {            internal ListEntry m_next;             internal T m_key;             internal Delegate m_handler;             public ListEntry(T key, Delegate handler, ListEntry next)             {                m_next = next;                m_key = key;                m_handler = handler;             }        }     }
      
     

我们就可以改变多个事件的使用方式，例子类似于下面这个。

public class DispatcherCore    {        readonly EventHandlerList
     
       Events = new EventHandlerList
      
       ();        public event EventHandler OnReceiveData {            add {                Events.AddHandler(EventType.ReceiveData, value);            }            remove {                Events.RemoveHandler(EventType.ReceiveData, value);            }        }        public event EventHandler OnRefreshData        {            add{                Events.AddHandler(EventType.RefreshData, value);            }            remove{                Events.RemoveHandler(EventType.RefreshData, value);            }        }        private void RaiseEvent(EventType eventType, EventArgs args)        {             var raiseEvent = Events[eventType] as EventHandler;            if (raiseEvent != null)                raiseEvent(this, args);        }        // 其它逻辑，在适当的时候调用RaiseEvent        private enum EventType        {            None,            ReceiveData,            RefreshData,            Error,            Info,        }    }