第1个回答 推荐于2017-09-04
as后面要接句子,所以一般是不会说as doing sth.的,你可以说as+主语+do/did/be doing...+sth.(e.g. I was thrilled as i saw he walk by.)
while doing sth.是有的,但是用这个句型的前提是,doing sth.的主语和主句的主语是一致的。(e.g. I always listen to music while doing my homework. 做作业和听歌的主语都是我,所以可以用)