public Message GetCollection(int current_page, int per_page, bool vpn_only, string ou)
        {
            try
            {
                current_page = current_page < 1 ? 1 : current_page;
                per_page = per_page < 1 ? 10 : per_page;
                ExchangeUserShorter users = new ExchangeUserShorter();
                string result = ExchangeRepo.GetUser("", current_page, per_page, vpn_only, HttpUtility.UrlDecode(ou));

                users = XmlSerializationHelper.Deserialize<ExchangeUserShorter>(result);

                return MessageBuilder.CreateResponseMessage(users);
            }
            catch (Exception e)
            {
                string message = "";
                while (e != null)
                {
                    message += e.Message;
                    e = e.InnerException;
                }
                return MessageBuilder.CreateResponseMessage(message);
            }
        }
        /// <summary>
        /// Method uses PowerShellSnapIn "Microsoft.Exchange.Management.PowerShell.Admin" to get user mailbox using CMDLET Get-Mailbox
        /// </summary>
        /// <param name="identity">User login name</param>
        /// <param name="current_page">Current Page to return</param>
        /// <param name="per_page">Entries to return per page</param>
        /// <param name="vpn_only">Return only VPN users, default is false</param>
        /// <returns>String, ExchangeUser XML serialized</returns>
        public string GetUser(string identity, int current_page = 1, int per_page = 10, bool vpn_only = false, string ou = "")
        {
            List<ExchangeUser> users = new List<ExchangeUser>();
            ExchangeUserShorter shorty = new ExchangeUserShorter() { CurrentPage = current_page, PerPage = per_page };
            int total_entries;

            try
            {
                users = GetUsers(out total_entries, identity:identity, displayName:"", current_page:current_page, per_page:per_page, vpn_only:vpn_only, ou:ou);
                shorty.users = users;
                shorty.TotalEntries = total_entries;
            }
            catch (Exception e)
            {
                return e.Message;
            }

            if (users.Count == 0){
                return XmlSerializationHelper.Serialize(shorty);
            }else if (identity.Trim() == ""){
                return XmlSerializationHelper.Serialize(shorty);// +"THEWORLDSLARGESTSEPERATOR" + total_entries.ToString();
            }else{
                return XmlSerializationHelper.Serialize(users[0]);
            }
        }