display list of customers

Hi,

i want to display list of customers in my database but an error has occured , please help me

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.ServiceModel;

using System.Data.SqlClient;

using System.Data.OleDb;

using System.Data;

namespace ClientServiceLibrary

{

    [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]

    public class ClientTopNetService  :  IClientTopNetService

    {

        #region IClientTopNetService Membres

        public ClientTopNet ConsultationClient(int ID_CLIENT)

        {

            System.Data.OleDb.OleDbConnection conn = new System.Data.OleDb.OleDbConnection();

            conn.ConnectionString = @"Provider=SQLOLEDB.1;Integrated Security=SSPI;Persist Security Info=False;User ID=topnet;Initial Catalog=TopnetBase;Data Source=SWEET-4B6F892B4\SQLEXPRESS";

            ClientTopNet oClients = new ClientTopNet();

            System.Data.OleDb.OleDbDataReader rs;

            System.Data.OleDb.OleDbCommand comm = new System.Data.OleDb.OleDbCommand("select * from client  where ID_CLIENT='"+ID_CLIENT+"'", conn);

            rs = comm.ExecuteReader();

            while (rs.Read())

            {

                ClientTopNet oClient = new ClientTopNet(); 

                oClient.LOGIN_CREATION = rs["LOGIN_CREATION"].ToString();

                oClient.NOM = rs["NOM"].ToString();

                oClient.ADRESSE= rs["ADRESSE"].ToString();

                oClients.Add(oClient);

              

                return oClients;

            }

}