text: public virtual SessionToken CheckForUpdate(string currentVersion){lock (padlock){EnsureOpen();if (currentRevision == null)return null; if (currentVersion != null && currentRevision.Revision.CompareTo(currentVersion) <= 0)return null; currentRevision.IncRef();string sessionID = sessionToken.IncrementAndGet().ToString();SessionToken token = new SessionToken(sessionID, currentRevision.Revision);sessions[sessionID] = new ReplicationSession(token, currentRevision);return token;}}