public InvoiceEditViewModel(string ID)
        {
            ID2 = ID;
            Proxy proxy = new Proxy();
            result = proxy.SearchInvoiceID(ID);
            foreach (var obj in result.Invoice)
            {
                InvoiceNum = obj.Nummer;
                string PayDate1 = obj.Faelligkeit;
                string EditDate1 = obj.Datum;
                Name = obj.Vorname + " " + obj.Nachname;
                BillingAdress = obj.Billingadress;
                Comment = obj.Kommentar;
                Note = obj.Nachricht;

                /* Rechungszeile 1 */
                Stk1 = obj.Menge1;
                Article1 = obj.Artikel1;
                Price1 = obj.Stueckpreis1;
                USt1 = obj.Ust1;

                /* Rechungszeile 2 */
                Stk2 = obj.Menge2;
                Article2 = obj.Artikel2;
                Price2 = obj.Stueckpreis2;
                USt2 = obj.Ust2;

                /* Rechungszeile 3 */
                Stk3 = obj.Menge3;
                Article3 = obj.Artikel3;
                Price3 = obj.Stueckpreis3;
                USt3 = obj.Ust3;

                string[] PayDateReg = Regex.Split(PayDate1, "T");
                PayDate = PayDateReg[0];

                string[] EditDateReg = Regex.Split(EditDate1, "T");
                EditDate = EditDateReg[0];

            }
        }