ashamed

be ashamed at, be ashamed of

这两个短语意思相近。它们的区别是：
ashamed at后面接的动名词必须是个非意愿性动词; ashamed of后面则不一定,可以是意愿性动词,也可以是非意愿性动词。例如：
I am ashamed at not writing you sooner.
我为没有早日给你回信感到惭愧。
The candidate was ashamed of his cheating in the English examination.
那考生为自己在英语考试中的作弊行 为而感惭愧。

be ashamed of v-ing, be ashamed to-v

ashamed可接动词不定式,也可接“of+动名词”。一般说来,动词不定式所表示的动作是还未发生的,而动名词所表示的动作则是已发生的。例如：
Aren't you ashamed to talk like that?
难道你讲得出这样的话吗?
Aren't you ashamed of talking like that?
难道你讲了那样的话却不觉得难为情?
She was ashamed to ask for help.
她耻于请求帮助。
She was ashamed of asking for help.
她为请求帮助而羞愧。

ashamed, shameful, shameless

ashamed的意思是“羞耻,惭愧”,故其主语是人,一般只用作表语; shameful的意思是“可耻的”,通常修饰事物或行为,既可作表语,也可作定语; shameless的语气最重,意思是“无耻的”,可修饰事物或行为,也可指人,在句中可以作表语,也可以作定语。例如：
I'm ashamed of myself for being so stupid.
我因自己这么愚蠢而感到惭愧。
Such shameful conduct should be stopped.
这种可耻的行为是不容许的。
He was so shameless that he said she loved him.
他竟这样的恬不知耻地说她爱他。