while 后面必须借动词的ing形式吗？

因为when 后面可以接短暂性动词~而while 后接的是一个动作的进行时~所以加ing

恩..While后面只可以跟随动词-ing的从句..when可以代替他..

这里用ing是用了动词的非谓语形式做伴随状语,这里用when代替也可以,when 后面也可以接这种结构.比如
The school master looked angrily at the naughty student while talking with his parents
也可以:
The school master looked angrily at the naughty student when talking with his parents
或
The school master looked angrily at the naughty student while he was talking with his parents.
注意这里的while是连词,这样用法比较少,一般习惯用when.

when是当什么什么的时候，最普通的一个词，几乎没有什么特殊要求，后面接什么都可以，凡是用while的都可以用when代替。
while也是当什么什么的时候，但后面要加持续一段时间的动作或状态，而瞬间的动作就不能用while来表达。
例如可以说I was eating dinner when he came in.
但不可以说I was eating dinner while he came in.(came不是持续的)
while后面也不一定要加ing的动词形式，也可以用表状态的词。
例如：I stayed in the hospital while he was ill.ill表状态。