Hi Helena,

Something like this should work:

TopicQuery q = new TopicQuery();
q.Room = new RoomCriterion();
q.Room.ID = new IntegerCriterion();
q.Room.ID.Includes = new IntegerInCriterion();

// Inlcude rooms with id 1, 7 and 23
q.Room.ID.Includes.Values.Add(1);
q.Room.ID.Includes.Values.Add(7);
q.Room.ID.Includes.Values.Add(23);

MessageCollection topics = 
QueryHandler.GetQueryResult<EPiServer.Community.Forum.Message, MessageCollection>(q, 1, 10, out itemCount);

Best Regards,
Tom

There is also the built in ForumHandler.GetTopics method that takes a RoomCollection as an argument. It will be quicker and you can use the specialised sort orders.

http://sdk.episerver.com/community/html/M_EPiServer_Community_Forum_ForumHandler_GetTopics.htm

/Mattias

Thanks a lot for your quick answers!

I think I need to use the query (?) since I want to filter on other properties as well, such as creation dates and number of topic replies.

Yep, that's correct. If you want to do more filtering you need to use the query system.

Best regards,
Tom