、。
Oh my, getting up from your seat in the middle of a meal goes against the rules of manners, you know.
Literal
Oh-my, meal [genitive-の] middle [at-に] seat [object-を] stand [as-for-とは] manner [to-に] go-against.
A mild scold. おやおや is a reduplicated interjection expressing mild surprise or gentle rebuke, often from an older or more authoritative speaker — similar to 'oh my,' 'well well.' The structure ~とは is a topic-framing particle that takes an action (here 席を立つ, 'standing up from one's seat') and marks it as the thing being evaluated: 'as for the act of X, [it is Y].' Often carries a slight note of judgment or surprise at the act itself. マナーに反する ('violate manners,' 'go against manners') is the standard collocation for 'being rude' in polite/formal register.