public SelfInvoiceViewModel() : base(NumberOfRowsInSelfInvoicesGrid) { _contoData = new ContoData(); ModifySelfInvoiceCommand = new RelayCommand(ModifySelfInvoiceCommand_Executed); UpdateSelfInvoiceCloseCommand = new RelayCommand(UpdateSelfInvoiceCommandClose_Executed); UpdateSelfInvoiceCommand = new RelayCommand(UpdateSelfInvoiceCommand_Executed); RemoveSelfInvoiceCommand = new RelayCommand(RemoveSelfInvoiceCommand_Executed); InvoiceDate = DateTime.Now; InvoiceYear = DateTime.Now.Year; VatExempt = true; Materials = new List <Material>(_contoData.MaterialsGet()); ExistingMaterials = new List <Material>(Materials); Measures = new List <Measures>(_contoData.MeasuresGet()); ExistingMeasures = new List <Measures>(_contoData.MeasuresGet()); Initialize(OnPropertyChanged, _contoData.SelfInvoicesMasterGet); UpdatePanelVisibility = Visibility.Collapsed; }