Hi
The relationship between a Campaign and a Marketing List is an n:n, so there is an intersect Entity you can check; 'campaignitem'
First step is to do a retrievemultiple on campaignitem records where the campaign has the same Id as the one you want to check, and from that retrievemultiple the Entity will also have an attribute for the MarketingList (although I dont know the name off
the top of my head, some tracing may be needed here)
Please note that you will only be able to retrieve the current members of a MarketingList, not the ones who were members when the campaign was created. If you want that, you'll need to look at the related Campaign Responses. Also, another thing to note is
that you will only be able to navigate to the members of a STATIC Marketing List as dynamic lists are calculated when needed, and so aren't stored anywhere (but you'll have the Id, which judging by your question should be fine)
Hope this helps!
