问题描述
是否有可能在执行 Place1
行时得到通知并执行 Place2
?
interface ICat
{
void StartWork();
public event EventHandler WorkDone;
}
class Cat : ICat
{
public event EventHandler WorkDone;
public void StartWork()
{
}
void OnUnsubscribed()
{
//Place2
}
}
class CatUser
{
CatUser()
{
var cat = new Cat();
cat.WorkDone += Cat_WorkDone;
cat.WorkDone -= Cat_WorkDone; //<--- Place1
}
private void Cat_WorkDone(object sender,EventArgs e)
{
}
}
解决方法
是的,事件对于委托就像属性对于支持字段一样。您可以将事件编写为
private EventHandler _workDone;
public event EventHandler WorkDone
{
add
{
// Event subscriber subscribes
_workDone += value;
}
remove
{
// Event subscriber unsubscribes
_workDone -= value;
}
}
事件通常是自动实现的,并在后台自动创建添加和删除访问器..
另见:
- How to implement custom event accessors (C# Programming Guide)
-
.NET Matters / Event Accessors (Microsoft Docs)(显示
Delegate.Remove
的示例,请参阅 @madreflection 的评论)。 - add (C# Reference)
- remove (C# Reference)
你应该这样做:
interface ICat
{
void StartWork();
event EventHandler WorkDone;
}
class Cat : ICat
{
public event EventHandler WorkDone;
public void StartWork()
{
}
void OnUnsubscribed()
{
//Place2
}
internal void UnSubscribe(System.EventHandler cat_WorkDone)
{
this.WorkDone -= cat_WorkDone;
OnUnsubscribed();
}
}
class CatUser
{
CatUser()
{
var cat = new Cat();
cat.WorkDone += Cat_WorkDone;
cat.UnSubscribe(Cat_WorkDone);
}
private void Cat_WorkDone(object sender,EventArgs e)
{
}
}