public MainViewViewModel(MainWindow view) { this.view = view; examPeriodTabs = new ObservableCollection <TabItem>(); foreach (var activeExamPeriod in ServiceDataProvider.GetActiveExamPeriods()) { examPeriodTabs.Add(new TabItem() { Header = activeExamPeriod.Name, Tag = activeExamPeriod.ExamPeriodId }); } Courses = ServiceDataProvider.GetProfessorCourses(4); students = new ObservableCollection <ExamRegistration>(); view.Tabcontrol.SelectedIndex = 0; view.cbxCourses.SelectedIndex = 0; view.OnSelectionComboBoxChanged = delegate { ProvideRegistredStudentsAndExamInfo(); }; view.OnSelectionTabControlChanged = delegate { ProvideRegistredStudentsAndExamInfo(); }; }