public AddWaybillLineFromCatalog()
{
InitFields();
DisplayName = "Добавление из каталога";
CurrentCatalog = new NotifyValue <Catalog>();
CatalogTerm = new NotifyValue <string>();
ProducerTerm = new NotifyValue <string>();
CurrentProducer = new NotifyValue <Producer>();
WasCancelled = true;
IsOkEnabled.Value = false;
CurrentCatalog.Changed()
.Merge(CurrentProducer.Changed())
.Merge(SupplierCost.Changed())
.Merge(Quantity.Changed())
.Subscribe(_ => IsOkEnabled.Value = CurrentCatalog.Value != null && CurrentProducer.Value != null && SupplierCost.Value > 0 && Quantity.Value > 0);
}