Close All Windows

[Tino]

I wrote this to prevent the user from closing the main dialog and leaving other windows open:

void Dialog::closeEvent(QCloseEvent *e) {
    if (QMessageBox::question(this, tr("Close ALL windows?"),
            tr("Close ALL windows?"), QMessageBox::Yes, QMessageBox::No) == QMessageBox::Yes)
    {
        qApp->closeAllWindows();
    }
}

void Dialog::closeEvent(QCloseEvent *e) {
    if (QMessageBox::question(this, tr("Close ALL windows?"),
            tr("Close ALL windows?"), QMessageBox::Yes, QMessageBox::No) == QMessageBox::Yes)
    {
        qApp->closeAllWindows();
    }
}

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But when I click yes nothing happens and the program is blocked.
What I do wrong?