private void btnUpdate_Click(object sender, RoutedEventArgs e) 
 { 
   xxxxxxx.Workflow1_WebServiceSoapClient zer = new xxxxx.Workflow1_WebServiceSoapClient(); 
        zer.demanderSubmitReportCompleted += new EventHandler<xxxxxxxxxxxxxxx.demanderSubmitReportCompletedEventArgs>(service2); 
        zer.demanderSubmitReportAsync("zzz", 20000); 

   }   

public void service2(object sender, xxxxx.demanderSubmitReportCompletedEventArgs e) 
{ 
        string a = e.Result; 
} 

I'm trying to call a windows workflow foundation published as a web service from a Silverlight project. When I call it from a console application it works fine because I can add a web reference then I just make an instance of that webservice then I invoke the method I want. The problem is in the silverlight project cause i can just add a service reference so I find myself working with soap stuff that doesn't work at all, and here is the code error:

here is the code error:i change it a litle bit in english

Error in exécution Microsoft JScript: Unhandled Error in Silverlight Application  exception happened in the operation, résult not valide. Consult InnerException for more information.   in System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
   in AEDSilverlightIntegrated.ServiceReference2.demanderSubmitReportCompletedEventArgs.get_Result()
   in AEDSilverlightIntegrated.SilverEntryAedHeaderNew.mmm_demanderSubmitReportCompleted(Object sender, demanderSubmitReportCompletedEventArgs e)
   in AEDSilverlightIntegrated.ServiceReference2.Workflow1_WebServiceSoapClient.OndemanderSubmitReportCompleted(Object state)