why not to do还是why not doing

why not to do 还是why not doing why not do还是why not doing? why not doing sth还是why not do sth还是why not to do sth Why not 后面+doing 还是to do? why not +doing还是do why not后加do还是doing还是to do? why not后面是doing sth还是 to do sth why not sb +do还是to do why not +什么 doing?do? "why not "后面加do还是to do还是doing?为什么?能不能具体点? Why not doing sth.make sb.to do sth. Why not _____a party this week?（后加have原形、to do形式、还是doing形式?