类型安全的EventHandlerList

我们写一个类时，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。经过我的一番改造，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：

 1 public sealed class EventHandlerList<T> : IDisposable  2     {  3         ListEntry head; 4  5         public EventHandlerList()  6         { } 7  8         public Delegate this[T key] 9         {10             get{ 11                 ListEntry e = Find(key);12                 return e == null ? null : e.m_handler;13             }14             set{15                 ListEntry e = Find(key);16                 if (e != null){17                     e.m_handler = value;18                 } 19                 else {20                     head = new ListEntry(key, value, head);21                 }22             }23         }24 25         public void AddHandler(T key, Delegate value) 26         {27             ListEntry e = Find(key); 28             if (e != null) {29                 e.m_handler = Delegate.Combine(e.m_handler, value);30             }31             else { 32                 head = new ListEntry(key, value, head);33             } 34         } 35 36         public void AddHandlers(EventHandlerList<T> listToAddFrom) 37         {38             ListEntry currentListEntry = listToAddFrom.head;39             while (currentListEntry != null) { 40                 AddHandler(currentListEntry.m_key, currentListEntry.m_handler);41                 currentListEntry = currentListEntry.m_next; 42             } 43         }44  45         public void Dispose() 46         { 47             head = null;48         } 49  50         private ListEntry Find(T key) 51         {52             ListEntry found = head; 53             while (found != null) {54                 if (found.m_key.Equals(key)) {55                     break;56                 } 57                 found = found.m_next;58             } 59             return found; 60         }61  62         public void RemoveHandler(T key, Delegate value) 63         {64             ListEntry e = Find(key); 65             if (e != null) {66                 e.m_handler = Delegate.Remove(e.m_handler, value);67             } 68         }69  70         private sealed class ListEntry 71         {72             internal ListEntry m_next; 73             internal T m_key; 74             internal Delegate m_handler;75  76             public ListEntry(T key, Delegate handler, ListEntry next) 77             {78                 m_next = next;79                 m_key = key;80                 m_handler = handler; 81             }82         } 83     }

有了它，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。

 1 public class DispatcherCore 2     { 3         readonly EventHandlerList<EventType> Events = new EventHandlerList<EventType>(); 4  5         public event EventHandler OnReceiveData { 6             add { 7                 Events.AddHandler(EventType.ReceiveData, value); 8             } 9             remove {10                 Events.RemoveHandler(EventType.ReceiveData, value);11             }12         }13 14         public event EventHandler OnRefreshData15         {16             add{17                 Events.AddHandler(EventType.RefreshData, value);18             }19             remove{20                 Events.RemoveHandler(EventType.RefreshData, value);21             }22         }23 24         private void RaiseEvent(EventType eventType, EventArgs args)25         { 26             var raiseEvent = Events[eventType] as EventHandler;27 28             if (raiseEvent != null)29                 raiseEvent(this, args);30         }31 32         // 其它逻辑，在适当的时候调用RaiseEvent33 34         private enum EventType35         {36             None,37             ReceiveData,38             RefreshData,39             Error,40             Info,41         }42     }

用起来更方便，很难出错。希望对大家有用。