When executing the following query:

var roomQuery = new RoomQuery
            {
                Forum =
                    new ForumCriterion
                    {
                        ID = new IntegerCriterion { Value = Properties.Settings.Default.RootForumId }
                    }
            };

roomQuery.LastChangedTopic = new TopicCriterion {Created = new DateTimeCriterion()};
                    roomQuery.OrderBy.Add(new CriterionSortOrder(roomQuery.LastChangedTopic.Created, SortingDirection.Descending));

var rooms = ForumHandler.Instance.GetQueryResult(roomQuery, page, pageSize, out totalItems);

and then rendering the results in a template (in my case a Razor view):

@foreach (var room in Model.Rooms)
{
    
    
            
@room.Header.FormatOrEncodeContentText() (@room.NumReplies)
            
Last updated @room.FormatLatestPostDate()
        
    
}

it appears that the results of the query are cached (for an indeterminate amount of time) but the derived value for "Date of Last Post" is not, e.g.

public static string FormatLatestPostDate(this RoomBase room)
        {
            if (room.LastChangedTopic != null)
            {
                var last = room.LastChangedTopic.LastReply;
                if (last != null)
                {
                    return last.Changed
                        ? last.Modified.FormatTimeSince()
                        : last.Created.FormatTimeSince();
                }

                return room.LastChangedTopic.Changed
                    ? room.LastChangedTopic.Modified.FormatTimeSince()
                    : room.LastChangedTopic.Created.FormatTimeSince();
            }

            return string.Empty;
        }

(code modified from Rooms.ascx.cs GetDateOfLatestPost(RoomBase room) method).

The result is that after a topic update, my displayed list shows the rooms in the same order as before the update, yet the "Last Updated" field IS up-to-date, meaning my list looks out of order.

So the question is, is there any way to:

1. Flush the cache for my RoomQuery manually?

2. Cache the LastChangedTopic with a dependency on the RoomQuery cache key?