[Resolvido] Erro Must declare the scalar variable "@idClient&

Sou iniciante em c# e estou tentando listar dados em uma grid e esta dando seguinte erro: Erro Must declare the scalar variable "@idClient"

Código na DAL:

public static List<OM.Ura.Client> LoadClient(int idClient)
{

 string sql;
 sql = @"select nr_extension,nm_attendant from service.client_attendant ca
 inner join service.attendant a on a.id_attendant = ca.id_attendant
 where id_client = @idClient";

 Database db = DatabaseFactory.CreateDatabase("Registration");
 DbCommand dbCommand = db.GetSqlStringCommand(sql);

 CreateParam(dbCommand, "@id_client", DbType.Int32, idClient);

 List<OM.Ura.Client> ret = new List<OM.Ura.Client>();
 using (IDataReader dataReader = db.ExecuteReader(dbCommand))
 {
 while (dataReader.Read())
 {
 OM.Ura.Client objclient = new OM.Ura.Client();
 OM.Ura.Group objGroup = new OM.Ura.Group();
 OM.Ura.Attendent objattendant = new OM.Ura.Attendent();

 objclient.CdClient = Convert.ToInt32(dataReader["CD_STOCK_EXCHANGE"]);
 objclient.IdClient = Convert.ToInt32(dataReader["id_client"]);
 objclient.NmClient = dataReader["nm_client"].ToString();

 objclient.GroupInfo = objGroup;
 objclient.AttendentInfo = objattendant; //fazer o attendent igual ai group (feito).
 }

 }

 return ret;
 }

EVENTO BOTÃO:

protected void btnRelClient_Click(object sender, EventArgs e)
{
if (string.IsNullOrEmpty(TxtCodRelClient.Text))
{

 ShowAlert("Por favor, digite algo válido (Letras e Números).");
 }

 else
 {
 int id;
 if (int.TryParse(TxtCodRelClient.Text, out id))
 {
 List<Lib.OM.Ura.Client> clients = Lib.BLL.Ura.LoadClient(id);
 try
 {
 if (clients.Count > 0)
 {

 GridViewClientgroupaTTendant.DataSource = clients;
 GridViewClientgroupaTTendant.DataBind();

 }
 else
 {
 ShowAlert("Não existe cliente relacionado a este atendente. ");

 }
 }
 catch (Exception ex)
 {

 ShowAlert(ex.InnerException.ToString());
 }
 }
 }
 }

MINHA GRID:

<asp:TabPanel runat="server" HeaderText="Relatório de Cliente" ID="TabPanel1">

 <ContentTemplate>
 <asp:Label ID="lblrelCli" runat="server" Text="Digite Código do cliente:"></asp:Label>
 <asp:TextBox ID="TxtCodRelClient" runat="server" TextMode="MultiLine" width="360px" height="160px"></asp:TextBox>
 <asp:Button ID="btnRelClient" runat="server" Text="Procurar" OnClick="btnRelClient_Click"></asp:Button>
 <asp:GridView ID="GridViewClientgroupaTTendant" runat="server" AutoGenerateColumns="False" BackColor="White" BorderColor="#FF6600"
 BorderStyle="Solid" BorderWidth="2px" CellPadding="4" Width="100%">
 <Columns>
 <asp:BoundField DataField="CD_STOCK_EXCHANGE" HeaderText="Código Cliente"
 SortExpression="Códido" Visible="False" />
 <asp:BoundField DataField="id_client" HeaderText="Id do Cliente"
 SortExpression="Nome" Visible="False" />
 <asp:BoundField DataField="nm_client" HeaderText="Nome Cliente"
 SortExpression="Nome" />
 </Columns>
 </asp:GridView>
 </ContentTemplate>
 </asp:TabPanel>