I have a sdi program, db click on it will open a
dialogA,on dialogA , Ctrl+f will open a find sub
dialogB,on dialogB , when something not be found , it will
open a message dialogC, this time when I want close the
main window of the application ,  the dialogA and dialogB
can not be closed , I think maybe they call each
other ,that is dialogA open dialogB, and dialogB call
function of dialogA, and the time of I want to close the
main window just is when it have not return . How can I do
it ?