public void SetTaskStates(IEnumerable <ITaskState> taskStates) { if (TaskStates == null) { TaskStates = new ObservableCollection <ITaskState>(); } if (CheckableTaskStates == null) { CheckableTaskStates = new ObservableCollection <Checkable <ITaskState> >(); } if (taskStates != null) { TaskStates.Clear(); TaskStates.AddRange(taskStates); CheckableTaskStates.AddRange(Checkable.Create(taskStates, true)); } }