Not force closing all rooms may be a good idea

Websockets/RoomManager.cs

@@ -34,7 +34,10 @@ public class RoomManager : IRoomManager
     
     public void RemoveAllRooms()
     {
-        Rooms.Clear();
+        foreach (var room in Rooms.Where(room => room.Value.IsEmpty()))
+        {
+            Rooms.Remove(room.Key);
+        }
     }
 }