如何检查Application.Exit（）中的CancelEventArgs？

Question

In my WinForms app, I call Application.Exit() in certain circumstances.

Application.Exit() has an overload that looks like this:

Application.Exit(CancelEventArgs e)

And the documentation says that e "Returns whether any Form within the application cancelled the exit."

However, it's unclear to me how I could ever examine e . The method returns void, and e is not defined as an out variable. Am I supposed to be able to examine this?

Yes, I did look at other questions regarding Application.Exit(), but none of them address this. They address handling the event, not calling the method.

Answer 1

Instantiate a CancelEventArgs variable and test its Cancel property after call to the Application.Exit :

CancelEventArgs e = new CancelEventArgs();
Application.Exit(e);
if (e.Cancel)
{
    // Cancelled
}

Answer 2

The reason you can examine e is that e is a reference to the CancelEventArgs object you pass in the method call. A variable of a reference type does not contain its data directly; it contains a reference to its data. When you pass a reference-type parameter , in this case a reference to a CancelEventArgs object, the called method is able to use the reference to access properties of the CancelEventArgs object, and it may for example set e.Cancel to true .

After the method call completes, the story is the same: e is still a reference to the CancelEventArgs object you passed, and you may now examine its properties to establish whether any have been changed by the called method.

EDIT I see from your comment it's not yet clear, so consider this: passing e as ref would mean the called method could change e to refer to a different CancelEventArgs object. It has nothing to do with whether it can set properties in the existing CancelEventArgs object.