public string GetUserInfoListByGroup(string groupID)
    {
        if (!header.VerifyCredentials(header.UserName, header.Password, header.Type))
        {
            return(string.Empty);
        }

        Guid gGroupID = (Guid)XmlSerializer.Deserialize(groupID);

        string url = System.Configuration.ConfigurationManager.AppSettings["WSAF.PhotoUrl"];

        User[] users = OrganizationPublicHelper.GetUserInfoListByGroup(gGroupID, false);

        foreach (User user in users)
        {
            if (!string.IsNullOrEmpty(url) && !string.IsNullOrEmpty(user.Photo))
            {
                user.Photo = url + user.Photo;
            }
        }
        return(XmlSerializer.Serialize(users));
    }