public void Active()
        {
            ClassRoom Classes = new ClassRoom();
            char      askToContinue;
            var       enterChoice = new EnterInformation();
            var       interFace   = new InterfaceOfUser();
            int       optionItem;
            int       isStudentExist;
            string    userInput;

            do
            {
                interFace.MainMenu();
                do
                {
                    userInput  = enterChoice.EnterUserInput();
                    optionItem = interFace.CheckAndReturn(userInput);
                } while (optionItem == -1);
                switch (optionItem)
                {
                case 1:
                    Console.Clear();
                    Classes.GetInformationOfGroup();
                    break;

                case 2:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist != 0)
                    {
                        Classes.FuntionCheckInformation();
                        break;
                    }
                    else
                    {
                        break;
                    }

                case 3:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist == 0)
                    {
                        break;
                    }
                    else
                    {
                        Classes.FindByID();
                    }
                    break;

                case 4:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist == 0)
                    {
                        break;
                    }
                    else
                    {
                        Classes.FindStudentsHaveHighestAverageGrade();
                    }
                    break;

                case 5:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist == 0)
                    {
                        break;
                    }
                    else
                    {
                        Classes.FindFailGrade();
                    }
                    break;

                case 6:
                    Console.Clear();
                    Classes.GetInformationASingleStudent();
                    break;

                case 7:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist == 0)
                    {
                        break;
                    }
                    else
                    {
                        Classes.CalculateAverages();
                    }
                    break;

                case 8:
                    Console.Clear();
                    isStudentExist = interFace.CheckStudentExist(Classes.Students.Count);
                    if (isStudentExist == 0)
                    {
                        break;
                    }
                    else
                    {
                        Classes.DeleteStudentById();
                    }
                    break;

                case 0: Console.Clear(); Console.Write("DONE"); break;

                default: Console.Clear(); Console.WriteLine("ERROR"); break;
                }
                askToContinue = interFace.CheckToContinue(optionItem);
            } while (optionItem != 0 && askToContinue == 'y');
        }