datacontext linq refresh example C# - linq example how to save object in linq to sql

        public string  SaveInvoiceXML(string sInvoice){
           try{
            Invoice inv = new Invoice();
            inv = CXMLConv.fromXML<Invoice>(sInvoice, inv);

            LinqDataObjectsDataContext dc = new LinqDataObjectsDataContext();

            dc.Invoices.Attach(inv);
            dc.Refresh(RefreshMode.KeepCurrentValues, inv);
            dc.SubmitChanges();

            return OK(CXMLConv.toXML(inv));
           }
           catch (Exception ex)
           {
               return RegisterError(ex, "SaveInvoiceXML", sInvoice);
           }
        }

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