You can simply say:“这不像你啊", or you also can say:"这不是你的风格" “风格”here means the way one usually acts or deals with things. We seldom use "作风" in our oral Chinese. This word is more formal, which often appears in political articles.

作风 = 做事风格 = to do things + style = the way someone does something. 风格 = style, method. Examples: 不理我不像你的风格。 You want to tell him/her: It was not your style which you ignored me. 作风 is used to describe someone, who has certain identical behaviors or habits, and either in a good way or a bad way. Example: 1. He started to take drugs, and that's not his 作风。 2. He has some problem with his 作风, for he took drugs recently. 风格, just means style,method. Example: 1. This carpet is of Asian 风格. 2. I wouldn't tell lies to you; that's not my 风格. 3. This famous painter did a unique picture of 风格 last week.(Which means that picture is different form his original 风格.)

You aslo could say "这还是你吗!".

calm down

这真不像是你的作为(formal)！ 这真不像是你会做出来的事！ If translate 'That's not like you' into“这真不像你" will be misundersood as "It doesn't like you (in this photo or sth. like that)." 风格unsually used to mean 1)the way a person always acts. or 2) the style of a master 作风 usually means the 1), and it's a commendatory term 风作_No such a term 作为refers to the thing a person done