private void Add()
 {
     SupplierPurchaseRequest.Raise(new SupplierPurchaseConfirmation(Supplier.ID),
                                   x =>
     {
         if (x.Confirmed)
         {
             Items.Add(x.SupplierPurchase);
             SelectedItem = x.SupplierPurchase;
             FixData();
         }
     });
 }
 private void Update()
 {
     SupplierPurchaseRequest.Raise(new SupplierPurchaseConfirmation(SelectedItem, _purchaseService.GetPurchaseDetails(SelectedItem.ID)),
                                   x =>
     {
         if (!x.Confirmed)
         {
             DataUtils.Copy(SelectedItem, _purchaseService.FindPurchase(SelectedItem.ID));
         }
         else
         {
             FixData();
         }
     });
 }