c# Web Service NullReferenceException

Živijo!

Imam spodnjo metodo, in mi vrača Exception:

System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at TestWS.createReq(CreateReq CreateReq) in c:\TestWS\TestWS.asmx:line 109
--- End of inner exception stack trace --

Morda kdo ve v čem je težava?

public partial class CreateReq
{
public string input;
}
public partial class CreateResp
{
public Rezultat Rezultat;
}

public partial class Rezultat
{
public int vrednost;
public string opis;
}

[WebMethod(Description = "CreateRequest", CacheDuration = 0, BufferResponse = false)]
[SoapDocumentMethodAttribute(ParameterStyle = SoapParameterStyle.Bare)]
[return: XmlElement("CreateResp")]
public CreateResp createReq(CreateReq CreateReq)
{
CreateResp res = new CreateResp();
CreateReq req = createReq;

res.Rezultat.vrednost = 0;
res.Rezultat.opis = "OK";

return res;
}

deluje tnx ;)