I need some help to understand lambad expresion

Question

I know this might sound very stupid but can someone explain to me why the following code do not work? and maybe some tutorial for dummie on lambad:

int test = 1;
        int testLambadIndex = rooms.FindIndex (r => (Room.LastCreatedRoomAt)r.lastCreatedRoomAt = (Room.LastCreatedRoomAt)test);

i try to use this enum from Room class 

public enum LastCreatedRoomAt{North = 1,South,West,East,None};

rooms is a list of type Room.