private void OnSortByTeacherAndDepartment(object Parameters) { var values = (object[])Parameters; ComboBox Teacher = values[0] as ComboBox; ComboBox Department = values[1] as ComboBox; try { ObservableCollection <GetInfoDiscipline_Result> a = new ObservableCollection <GetInfoDiscipline_Result>(); ObservableCollection <SortDisciplinebyTeacherAndDepartment_Result> ab = new ObservableCollection <SortDisciplinebyTeacherAndDepartment_Result>(ST.SortDisciplinebyTeacherAndDepartment(Teacher.SelectedItem.ToString(), Department.SelectedItem.ToString()).ToList()); foreach (SortDisciplinebyTeacherAndDepartment_Result k in ab) { // a.Add(k as GetInfoDiscipline_Result); } ListDiscipline = new ObservableCollection <GetInfoDiscipline_Result>(a); } catch { } }