I should have done this.
I should have been done this.
I should have been to do this.
I have not too much idea about english but I want to know that, grammatically above sentences are correct or not? Please someone let me know.
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The first sentence, 'I should have done this', is a grammatically correct sentence, meaning that I regret not having done something. Neither of the other two sentences would be spoken by a native English speaker.