Gui hangs when close button is clicked

Hello,
I am a newbie in Qt.I would like to close a window but the Qt Gui hangs when I do so.
I am trying to close the Gui with this->close()

Code:

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connect(ui->Close, SIGNAL(clicked()), this, SLOT(close()));

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Code:

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void MainWindow::close()
{
    this->close();
}

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Can anybody tell me how to close the Gui without hanging it.

Code:

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#include <QApplication>
 
connect(ui->Close, SIGNAL(clicked()), qApp, SLOT(quit()));
 
or
 
connect(ui->Close, SIGNAL(clicked()), qApp, SLOT(closeAllWindows()));

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