Closing a form :)

[Cristoff]

I cannot figure out how to ask the user for input if a form should be closed (or application exited), when alt+f4 or the X button is clicked? Is there an event being fired when the user clicks the X button (the one on the caption bar)?

[leppie]

Subscribe to the Form.Closing event :) top secret xacc-ide 0.0.1

[Cristoff]

OK :) I have actually found out how it is done. Here is what a I did (nothing specially, really). I happens to me too often the solution is obvious but I miss it. buttonExit_Click... etc... is an event handler... is it how you are going to do it? Thanx

	private void buttonExit\_Click(object sender, System.EventArgs e)
	{
		// Raises the System.Windows.Forms.Form.Closing event
		this.OnClosing(new System.ComponentModel.CancelEventArgs());	
	}
	
	private void FormOfficeTools\_Closing(object sender, System.ComponentModel.CancelEventArgs e)
	{
		System.Windows.Forms.DialogResult result =
			System.Windows.Forms.MessageBox.Show(this,
			"Желаете ли да излезете от програмата?",
			"Изход от програмата",
			System.Windows.Forms.MessageBoxButtons.YesNo,
			System.Windows.Forms.MessageBoxIcon.Question
			);				 
		if (System.Windows.Forms.DialogResult.Yes == result)
			Application.Exit();
		else
		    // If "No" then cancel the System.Windows.Forms.Form.Closing event
			e.Cancel = true;
				
	}
	#endregion

[Cristoff]

sure but i've just missed that the System.ComponentModel.CancelEventArgs.Cancel property has to be set to true BTW is this call a good idea:

this.OnClosing(new System.ComponentModel.CancelEventArgs());

Here I raise the System.Windows.Forms.Form.Closing event, when a button Quit is clicked on (or another exit condition is met).

[Heath Stewart]

You don't need to call Application.Exit (in fact, I recommend you don't). The only condition you have to worry about is anything that would lead you to set CancelEventArgs.Cancel to true. If you don't set it, the form will continue closing as normal. The .NET Framework SDK even has a good example for the Form.Closing event.

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[Cristoff]

Thank you, Heath Stewart What's wrong with Application.Exit? Why don't you recommend using it? How should I then quit an application? I'm looking for the Form.Closing event... :) and still can't find it.

[Heath Stewart]

Because the form is already closing. If the form is your main form - the one you passed to Application.Run, once it's closed the application will exit anyway. There may already be messages in the pump that were posted that may need to clean-up resources. Calling Application.Exit circumvents that. So, if you don't set CancelEventArgs.Cancel to true, the form will close and the application will exit just as if you hadn't handled the Form.Closing event. And what do you mean you can't find it? It's documented in the .NET Framework SDK, and if you use the designer you can click the "Events" button in the PropertyGrid when your form is selected, find the Closing event and double-click it. You can also use IntelliSense. The thing is, you're not looking for Form.Closing, you're looking for this.Closing or _form1_.Closing or whatever is appropriate for accessing your instance of your form. Some basic understanding of programming is assumed. Closing is an instance event, so it will be defined for an instance of your form (so access it using this or a variable that refers to your Form).

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[Cristoff]

Sorry, I have meant the Form.Closing sample you have mentioned about and not the event! I have made a pretty stupid mistake and haven't checked what I have written. I understand about Application.Exit now. I thought that it isn't generally a good idea to use Application.Exit at all. BTW I have replaced Application.Exit with:

private void buttonExit_Click(object sender, System.EventArgs e)
{
this.Close(); // Close the main form and exit the application
}

Then I handle the Form.Closing event to ask the user if he really wants to quit etc. Is it a good idea or not? :) It seems to me like an implementation of your idea.

[Heath Stewart]

Yes, that is the way to handle it. Form.Close will send the Windows messages to close the Form. You're handling the WM_CLOSING message and optionally cancelling it. If you don't, the Form continues to close. When it's closed, if the message pump was waiting on it (i.e., you passed an instance of that Form to Application.Run), then the application will exit.

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[Roman Rodov]

to Raise the Form.Closing event you need to just call: this.Close();

[mikker_123]

Yes there is... it's called Closing... and when you handle it you can do all kind of stuff (including cancellation of closing) with it ;)