C＃匿名方法/块？

Question

I cannot understand this piece of code what is the "ViewDissapearing"? And what about "add" and "remove" blocks?

public event EventHandler ViewDisappearing;

public event EventHandler ViewDissapearing {
    add {
        ViewDisappearing += value;
    }
    remove {
        ViewDisappearing -= value;
    }
}

Answer 1

This is done to provide two names for the same event. "ViewDissapearing" is how the event was previously wrongly named, and all existing code that subscribes to the "ViewDissapearing" event is instead rerouted to subscribe to the new correctly spelt "ViewDisappearing" event instead.

The add { ... } block is executed when someone calls ViewDissapearing += ... , which does nothing more than ViewDisappearing += that same ... . Similarly for the remove { ... } block and -= .

Answer 2

This is to allow other code to attach to this event. This is the same idea as the Get / Set Property of a variable. For Events it is Add / Remove. As with Properties of variables, you can use the Variable directly, or you can use an Property. You usually use the Properrty if you want to add some custom code when adding a event.

Answer 3

这明确说明了编译器通常为类中的事件自动生成的内容。