Help with Gtk::MessageDialog

["Jamiil Abduqadir" <jalqadir gmail com>]

I have a class that derives from 'Gtk::MessageDialog', the class
displays a message box with an 'OK' button, the class is working just
fine, however, I don't know how to write a 
namespace jme{
class GtkmmException : public virtual Gtk::MessageDialog{ 
private:
   jme::Exception* ex;

protected:
public:
GtkmmException(Glib::ustring&, jme::Exception&);

~GtkmmException();

virtual void btnClicked();
}; // class
}  // namespace