Application Web e Web Servoces NAV

I created an application web and I want insert a New Customer in NAV
I published a Page 21 "Customer CARD "

Source application WEB

public Customer_Card Insert(NAVUser user, Customer_Card obj)

{

if (user == null || string.IsNullOrEmpty(user.UserName) || string.IsNullOrEmpty(user.Password) || string.IsNullOrEmpty(user.ResourceCode)) return null;
// WebService instance and set credentials of user that made the request
Customer_Card_Service.Customer_Card_Service wsInstance = new Customer_Card_Service.Customer_Card_Service();
wsInstance.Credentials = new NetworkCredential(user.UserName, user.Password);
wsInstance.Create(ref obj);

// dispose of the WS instance

wsInstance.Dispose();
return obj;
}

I have this ERROR !!!!!

Integer must not be blank. Integer is missing or invalid in the expression.
[LID:2:634158571611510188] - Integer must not be blank. Integer is missing or invalid in the expression. in System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) in System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodNameObject[] parameters) in It.Quidinfo.LutechNavAbstractionLayer.Customer_Card_Service.Customer_Card_Service.Create(Customer_Card& Customer_Card) in C:\TFS-REPOSITORY\Lutech\LutechNavPortal\DataAccessLibrary\Web References\Customer_Card_Service\Reference.cs:riga 208 in It.Quidinfo.LutechNavAbstractionLayer.ClienteProvider.Insert(NAVUser user, Customer_Card obj) in C:\TFS-REPOSITORY\Lutech\LutechNavPortal\DataAccessLibrary\ClienteProvider.cs:riga 34 in It.Quidinfo.LutechNavWebPortal.Src.Session.SessionManagement.ClienteBean.Crea(Customer_Card obj) in C:\TFS-REPOSITORY\Lutech\LutechNavPortal\LutechNavWebPortal\Src\Session\PagesSessionManagement\ClienteBean.cs:riga 25 in It.QuidInfo.LutechNavWebPortal.Private.FormCliente.Salva() in C:\TFS-REPOSITORY\Lutech\LutechNavPortal\LutechNavWebPortal\Private\FormCliente.aspx.cs:riga 60


Someone help me !!!!

Thanks ..