假设我监听一个事件:
Subject.NewEvent += delegate(object sender, NewEventArgs e)
{
//some code
});
现在如何取消注册此活动?或者只是让内存泄漏?
假设我监听一个事件:
Subject.NewEvent += delegate(object sender, NewEventArgs e)
{
//some code
});
现在如何取消注册此活动?或者只是让内存泄漏?
为您的匿名委托实例命名:
EventHandler<NewEventArg> handler = delegate(object sender, NewEventArgs e)
{
//some code
};
Subject.NewEvent += handler;
Subject.NewEvent -= handler;
如果您需要注销事件,我建议避免事件处理程序的匿名委托。
这是将其分配给本地方法更好的一种情况 - 您可以干净地取消订阅事件。
要在第一次调用时删除处理程序:
//SubjectType Subject = ..... already defined if using (2)
EventHandler handler = null;
handler = delegate(object sender, EventArgs e)
{
// (1)
(sender as SubjectType).NewEvent -= handler;
// or
// (2) Subject.NewEvent -= handler;
// do stuff here
};
Subject.NewEvent += handler;
您可以创建从所有事件侦听器注销的方法。这并不完全是您想要的,但有时它可能会有所帮助。例如(这确实有效=)):
class Program {
static void Main(string[] args) {
A someClass = new A();
someClass.SomeEvent += delegate(object sender, EventArgs e) {
throw new NotImplementedException();
};
someClass.ClearEventHandlers();
someClass.FireEvent();
Console.WriteLine("No error.");
}
public class A {
public event EventHandler SomeEvent;
public void ClearEventHandlers() {
Delegate[] delegates = SomeEvent.GetInvocationList();
foreach (Delegate delegate in delegates) {
SomeEvent -= (EventHandler) delegate;
}
}
public void FireEvent() {
if (SomeEvent != null) {
SomeEvent(null, null);
}
}
}
}
您需要匿名函数的名称,然后,只要名称在范围内,您就可以这样做:
var handler = new EventHandler(delegate(object o, EventArgs e)
{
//do something...
};
Subject.NewEvent += handler;
// later on while handler is still in scope...
Subject.NewEvent -= handler;
您是否需要出于泄漏以外的原因取消注册?
关于“或者只是允许内存泄漏”位,当垃圾收集器清理主题时,你的匿名委托也应该被清理,所以不应该有泄漏。
还有另一个(我的)问题在一些(太多)细节中涉及到这个问题:Weak event handler model for use with lambdas。