在变量闭包的情况下取消订阅事件

Question

I'm always try to unsubscribe events where it possible and may. In case when variable closure happen I do the following :

int someVar;

EventHandler moveCompleted = null;
moveCompleted = delegate(object sender, EventArgs e)
{
    //...
    //here is variable closure
    someVar = 5;
    //...
    moveStoryboard.Completed -= moveCompleted;
};

moveStoryboard.Completed += moveCompleted;

But I don't want to use anonymous method and I think this is not good way. Please give me some advice or code samples.

Thanks in advance.

Answer 1

If you don't want to use an anonymous function, it's much easier:

moveStoryboard.Completed += HandleStoryboardCompleted;

...

private void HandleStoryboardCompleted(object sender, EventArgs e)
{
    // Do stuff...
    moveStoryboard.Completed -= HandleStoryboardCompleted;
}

That will actually create another instance of EventHandler each time the method is called, but because that instance will be equal to the one used to subscribe (same method with the same target) it will be fine to use for unsubscription.

Answer 2

whats wrong with:

class MyClass
{
    public event EventHandler MyEvent;

    public MyClass()
    {
        MyEvent += OnSomeEventHandlerToMyLocalClassWhichOfcourseIsABadPractice;
    }

    protected void OnSomeEventHandlerToMyLocalClassWhichOfcourseIsABadPractice(object sender, EventArgs e)
    {
        MyEvent -= OnSomeEventHandlerToMyLocalClassWhichOfcourseIsABadPractice;
    }
}