public void AddMachine() { if (_windows.ShowDialog(IoC.Get <AddMachineViewModel>()) == true) { // TODO: Donesn't work! //foreach (var newMachine in _machines.Find(x => Machines.All(y => x.Id != y.Id)).ToList()) foreach (var newMachine in _machines.FindAll().Where(x => Machines.All(y => x.Id != y.Id)).ToList()) { Machines.Add(new MachineViewModel(newMachine, _machines)); } NotifyOfPropertyChange(() => Machines); } }