"don't expect me to be all dear diary this and dear diary that"
would you explain the meaning of that sentence and change the sentence in other word or form?
particularly, I have wondered the meaning of ~ "this" and ~ "that" and "be all"
This is a fairly common pattern of speech in English. It basically means that there is sickeningly too much of something or you're just taking things too far. The adverb all as presented in your example means complete, total or one hundred percent.
He's all about Apple computers. He just can't live without them. It's Apple computers this and Apple computers that all day long! Apple has become a religion for him!
Here, all means that he only likes Apple hardware. He is a one hundred percent, true-blue Apple-head.
He's a real Linux geek. Whenever I try to speak with him about computers, it's always the same tune: Linux this and Linux that. Like there are no other operating systems in existence.
Short Answer: "Don't expect me to care."
Long Answer: "Don't expect me to write in my diary about everything."
Longer Answer (including some assumptions): "Don't expect me to write in my diary about everything (that has happened between us) (because I don't even care that much)."
"To be all" is to be completely about something. For example,
Don't expect me to "Dear Diary" everything.
"This" and "that" are used as words to stand in as examples.
Don't expect me to be all "Dear Diary, this is what happened today. Dear Diary, this is what had happened yesterday."
"Dear diary" is just an expression people use to say that they had written something in their diary. For example,
Don't expect me to write in my diary about everything.
Without further context (and I'm guessing here), but I'm assuming the speaker is quite fed up with the other person and is possibly very hurt.
It sounds like a lot has happened between the two people and the other person was surprised that the speaker hadn't cared more, so the speaker is trying to express how much the speaker doesn't care.
The ironic thing is, the speaker does care, which is why the speaker is lashing out and using sarcasm.
But again, these are all just superficial analyses from watching too much TV and too many movies.
If you could give us some more context and let us know where you had heard this/seen this, we would be able to help you better.
Until then, hope this helps somewhat.