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<T> : 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<T> 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<EventType> Events = new EventHandlerList<EventType>(); 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,
}
}