Dialog box before closing

[Vansaj_Jain]

How can I add this functionality to xojo?

[Kem_Tekinay]

Use the Window.CancelClose event to present this dialog and react according to the result.

https://documentation.xojo.com/api/deprecated/window.html#window-cancelclose

[Ian_Kennedy]

Take a look at the MessageDialog class.
http://documentation.xojo.com/api/language/me.htmlssageDialog