static void Main(string[] args)
{
//int потому что нам нужно зарегистрировать изменения значения группы
//тип которого int => KeySelector должен быть int.
var first = new StudentCollection <int>((e) => e.Id, "first");
var second = new StudentCollection <int>((e) => e.Id, "second");
var j = new Journal <int>();
j.Subscribe(first);
j.Subscribe(second);
var s1 = new Student(Education.Bachelor, 5);
var s2 = new Student(Education.Bachelor, 5);
first.AddStudents(s1);
second.AddStudents(s2);
s1.Educ = Education.SecondEducation;
s2.Educ = Education.Specialist;
s1.Group = 4;
s2.Group = 1;
first.Remove(s1.Id);
second.Remove(s2.Id);
s1.Educ = Education.Specialist;
s2.Educ = Education.Bachelor;
s1.Group = 4;
s2.Group = 1;
// After deleting from Collections changing not write in journal
Console.WriteLine(j.ToString());
}
public void Subscribe(StudentCollection <TKey> a)
{
a.StudentsChanged += RegisterStudentChanged;
}