when doing 和 while doing 的区别

when doing:
when teacher came in the students were talking
while doing :
i was dancing while my sister was singing

前者是:
A在做什么(打电话等时间较多的事情)的时候,发生了一件事(短时间的,比如有一个很大的声音发出来了)
后者:
两者同时做,时间差不多的``

另外要注意，while有时还有转折意味。