lambda expression for exists within list

If I want to filter a list of objects against a specific id, I can do this:

list.Where(r => r.Id == idToCompare);   

What if, instead of a single idToCompare, I have a list of Ids to compare against?

What is the syntax for comparing against a predefined list? Something like:

int[] listofIds = GetListofIds();

list.Where(r => r.Id "in listofIds");