private void AddChild(object obj) { ChildViewModel viewModel = new ChildViewModel { Count = "1", IsAdd = true, Persons = ListsOfPersons, SelectedPerson = ListsOfPersons.FirstOrDefault() }; AddChildView view = new AddChildView { DataContext = viewModel }; Child newChild = new Child(); view.ShowDialog(); if (viewModel.IsConfirm) { newChild.child = viewModel.SelectedPerson; newChild.Count = Convert.ToDecimal(viewModel.Count); if (CheckIfValid(SelectedPerson, newChild)) { var res = db.AddChild(SelectedPerson, newChild); if (res == false) { MessageBox.Show("Wystąpił błąd przy dodawaniu!"); } Refresh(); } } }