static void Main(string[] args) { List <Student> students = new List <Student>(); StudentGroup studentGroup = new StudentGroup(students); var student1 = new Student("Percy Jackson"); var student2 = new Student("Melissa Hardwood"); var student3 = new Student("Rockie Balboa"); var student4 = new Student("Lara Croft"); var student5 = new Student(); var studentList = new List <Student>(); studentList.Add(student1); studentList.Add(student2); studentList.Add(student3); studentList.Add(student4); studentList.Add(student5); foreach (var student in studentList) { try { studentGroup.AddStudent(student); } catch (InvalidStudentInput e) { Console.WriteLine(e.Message); } } var newGroup1 = new List <Student>() { new Student("Alex Moreno"), new Student(), new Student("Sarah Svensson") }; var newGroup2 = new List <Student>(); try { studentGroup.AddGroup(newGroup1); } catch (Exception e) { Console.WriteLine(e.Message); } finally { PrintStudent(students); } try { studentGroup.AddGroup(newGroup2); } catch (Exception e) { Console.WriteLine(e.Message); } finally { PrintStudent(students); } Console.ReadKey(); }