/// <summary>
    /// Gets the user by ID.
    /// </summary>
    /// <returns>The user or null.</returns>
    /// <param name="personId">Person ID</param>
    public Person GetUserById(string personId)
    {
        if (userGroupId != initedGroupId)
        {
            GetOrGreateUserGroup();
        }
        if (userGroupId != initedGroupId)
        {
            return(null);
        }

        Person person = null;

        if (faceManager != null && !string.IsNullOrEmpty(userGroupId))
        {
            person = faceManager.GetPerson(userGroupId, personId);
        }

        return(person);
    }