In a Form I created, I've subscribed to the FormClosingEvent.
In this event I want to distinguish between a user that closes the form, or an outside OS event that closes the application. Therefor I read the CloseReason member of the FormClosingEventArgs. However it seems that when the user clicks on the OK button which is the Forms AcceptButton, the CloseReason seems to be set to "None". The same goes for the form's CancelButton.

Is this intended behaviour, and if not, should this not be documented?

When you handle the user clicking a close button that you have created on your form, you probably handle the application close with your own user code with a "this.Close();" command. When the form is actually closed with an Alt-F4 press or by clicking on the [X] - close button/box on the top-right corner, it is handled differently. Because the CloseReason field is ReadOnly, I am not sure how you would be able to make it so.

I would suggest that in your event handlers for the OK / Cancel button presses, you notify the other form of the impending "user-close" you will perform. Then in your other form where you see if the user closed the form, you can change the if statement to be:

if(e.CloseReason == CloseReason.UserClosing || userClose)
{
...
}

"userClose" will just be a boolean value that you change to true if the OK / Cancel button was pressed, and before you close that form.

I looked up the CloseReason enumeration on this page: MSDN CloseReasonand determined that the possible close reasons are:

	Member name	Description
	ApplicationExitCall	The Exit method of the Application class was invoked.
	FormOwnerClosing	The owner form is closing.
	MdiFormClosing	The parent form of this multiple document interface (MDI) form is closing.
	None	The cause of the closure was not defined or could not be determined.
	TaskManagerClosing	The Microsoft Windows Task Manager is closing the application.
	UserClosing	The user is closing the form through the user interface (UI), for example by clicking the Close button on the form window, selecting Close from the window's control menu, or pressing ALT+F4.
	WindowsShutDown	The operating system is closing all applications before shutting down.

I think in your case, you have a child form with an accept and cancel button, which caused the close. So it is not an ApplicationExitCall, as the application itself did not close. It's not a FormOwnerClosing or MdiFormClosing, since its owning form did not close. The Task Manager did not close the application. The user did not close using Alt-F4 or the Close Button. AndWindows did notclose the app, so it would fall under "none".

The description of the UserClosing event does not suggest that it only works with the window's close button or Alt+F4. It explicitly says that it is justan example.

The user is closing the form through the user interface (UI),

Does that not also includes my own controls? And if not, is there any way to make it so?

When you handle the user clicking a close button that you have created on your form, you probably handle the application close with your own user code with a "this.Close();" command. When the form is actually closed with an Alt-F4 press or by clicking on the [X] - close button/box on the top-right corner, it is handled differently. Because the CloseReason field is ReadOnly, I am not sure how you would be able to make it so.

I would suggest that in your event handlers for the OK / Cancel button presses, you notify the other form of the impending "user-close" you will perform. Then in your other form where you see if the user closed the form, you can change the if statement to be:

if(e.CloseReason == CloseReason.UserClosing || userClose)
{
...
}

"userClose" will just be a boolean value that you change to true if the OK / Cancel button was pressed, and before you close that form.

it was something I thought more of as a workaround (now there are two "closing" state variables), but if it's the only way it'll have to do.

Thanks!

Edsger