I have a few objects that I'd like to send to the server, but I want to make sure that this is the only thread that moving the data from Stage to Upload. Is the following code valid in a multithreaded environment?

        List<CounterInternal> UploadToServer = new List<CounterInternal>();
        List<CounterInternal> StagingQueue = new List<CounterInternal>();
      lock (this.UploadToServer)
        lock (this.StagingQueue)
        {
            if (UploadToServer.Count == 0)
            {
                UploadToServer = StagingQueue.DoDeepCopyExtensionMethod();
                // is the following line valid given that I have a Lock() on it?
                StagingQueue = new List<CounterInternal>();
            }
        }
      }