c# - Best way to intercept closing of window? -

i'm looking best way intercept closing of window in software. example want intercept closure of form called "settings", , not mainwindow. vb.net of procedure simple, had call closing event, wpf can not understand why event not captured, , result, code inside not executed.

in form want intercept closing for:

    protected override void onclosing(system.componentmodel.canceleventargs e)     {         if(dontclose)         {             e.cancel = true;         }         base.onclosing(e);     } 

replace dontclose conditions not closing.