public void Select(IEnumerable <ElementModelViewModel> elementModels) { List <LightViewModel> selectedModels = new List <LightViewModel>(); foreach (var elementModel in elementModels) { List <LightViewModel> lvmList; if (_elementModelMap.TryGetValue(elementModel.ElementModel.Id, out lvmList)) { foreach (var lightViewModel in lvmList) { if (!lightViewModel.IsSelected) { lightViewModel.IsSelected = true; selectedModels.Add(lightViewModel); } } } } SelectedItems.AddItems(selectedModels); }